A simple thin film effective index analysis for first-order gratings in Si photonic waveguides is... more A simple thin film effective index analysis for first-order gratings in Si photonic waveguides is shown to provide highly accurate results for reflected and transmitted power spectrums as long as the waveguide remains single mode and non-radiating. A cover layer can be added to the grating region of a Si photonic waveguide to increase the strength of the grating, modify transition losses from the input waveguide to the grating waveguide region, and/or modify the width of the reflectivity spectrum. For a given grating period, the peak reflection and spectral width of the reflectivity decrease as the duty cycle is decreased or increased from ~50%. For both radiating and multimode structures, the coupling between all modes, power radiated towards the superstrate (upwards), power radiated downwards (substrate) and transmitted power analyzed by Floquet-Bloch, Eigenmode Expansion and Finite Difference Time Domain methods show excellent agreement. Coupling coefficients calculated using an...
We show that in an optical waveguide with no material losses at wavelengths near the second-order... more We show that in an optical waveguide with no material losses at wavelengths near the second-order Bragg condition, there exists two pairs of modes. One pair has identical propagation constants but have different attenuation coefficients, while a second pair with identical propagation constants (different from the first pair) and have different attenuation coefficients. The four attenuation coefficients may have either a positive value, representing power leaking out of a waveguide mode or a negative value, representing power from an external source leaking into a mode. Moreover, a mode with a positive (negative) attenuation before the second Bragg condition, has a negative (positive) attenuation after the second Bragg condition. Radiation near the second-order Bragg condition of a periodic waveguide typically occurs at an angle perpendicular or nearly perpendicular to the propagation direction of the waveguide because the scattering centers have a period equal to or close to the per...
An equivalent surface current method is used to derive an analytic expression that approximates t... more An equivalent surface current method is used to derive an analytic expression that approximates the coupling coefficient, reflectivity bandwidth and group velocity for coupling between identical and non-identical TE modes in an asymmetric three-layer waveguide with a sinusoidal grating at one waveguide interface. The analytic expression for the coupling coefficient agrees with expressions derived by two other methods for contra-directional coupling between identical modes. The results from the analytical expressions are compared to results from a numerically accurate Floquet-Bloch solution. The analytical expressions, which do not depend on which interface contains the grating, provides almost identical results obtained by the accurate solution for shallow grating depths and small index changes at the grating interface, a case typical of single-mode distributed feedback lasers. However, the accurate numerical solution, unlike the analytic solution, shows that in waveguides with only a large index step at the grating interface, increasing the grating depth can result in decreasing the coupling coefficient, a case typical of some distributed Bragg reflector lasers. In highly confined silicon photonic waveguides (large index steps at both interfaces), the analytic expression gives accurate results even for deep gratings. The derivation of the analytical expression for the coupling coefficient in this paper using the equivalent surface current method extends the application of the previous analytic formulas to non-identical mode coupling where the forward and backward modes are not identical, which has application to gratings in multi-mode broadened waveguide lasers and amplifiers.
2016 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), 2016
The reflectivity of forty-grating sections consisting of two grating periods is simulated. Close ... more The reflectivity of forty-grating sections consisting of two grating periods is simulated. Close difference of two gratings periods causes similarity of the reflectivity of forty-gratings and single gratings except for the phase shift phenomenon.
The electro-optic switching properties of injection-coupled coherent twodimensional grating-surfa... more The electro-optic switching properties of injection-coupled coherent twodimensional grating-surface-emitting laser arrays with multiple gain sections and quantum well active layers are discussed and demonstrated. Within such an array of injection-coupled grating-surface-emitting lasers, a single gain section can be operated as intra-cavity saturable loss element that can modulate the output of the entire array. Experimental results demonstrate efficient sub-nanosecond switching of high-power grating-surface-emitting laser arrays by using only one gain section as an intra-cavity loss modulator.
Various types of surface-emitting semiconductor lasers are reviewed along with their anticipated ... more Various types of surface-emitting semiconductor lasers are reviewed along with their anticipated applications. The recent progress in grating-coupled surface-emitting (GSE) lasers is particularly emphasized. Such GSE arrays have operated continuously to more than 3 W and pulsed to more than 30 W. They have obtained cw threshold current densities of under 140 A/em 2 with cw differential quantum efficiencies of 20 to 40% per surface. Linewidths in the 40 MHz range have been obtained with output powers of 100 to 250 mW. The arrays typically consist of 10-30 mutually injection-coupled gain sections with l0 laterally coupled ridge-guided lasers in each gain section. A single GalnAs strained-layer quantum well with a graded index separate confinement heterostructure geometry allows junction down mounting with light emission through the transparent GaAs substrate. A surface relief grating is used for feedback and outcoupling.
Planar photonic integrated circuits based on four-port couplers offer enhanced sophistication and... more Planar photonic integrated circuits based on four-port couplers offer enhanced sophistication and functionality. Each four-port coupler is characterized by sixteen signal coupling coefficients governed by ten energy constraints. The ability to generate the constrained sixteen coupling coefficients is needed in the analysis of the four-port coupler. However, the energy constraint equations are nonlinear and cumbersome to solve directly. We introduce two techniques to reduce these signal coupling coefficients to a set of six free parameters. Hence we can characterize all possible couplers in terms of their sixteen constrained coupling coefficients, or either of two sets of six free parameters. This reduction in parameters has significant ramifications for the design, specification, and empirical characterization of these useful building blocks.
This paper investigates the effect of a high-refractiveindex layer added onto the clad layer of a... more This paper investigates the effect of a high-refractiveindex layer added onto the clad layer of an optical waveguide. With proper design, the value of the fundamental mode's confinement factor in the added layer can exhibit a resonance. This resonance depends on the added layer's location, thickness, complex index, and wavelength of operation. If loss is incorporated into this added layer, relatively small changes in waveguide properties can result in large changes in loss. This phenomenon is referred to in this paper as the resonant-layer effect (RLE). A number of devices, including isolators, polarizers, and modulators, can be made and/or improved by using the RLE. As examples, this paper describes an integratable isolator giving 240-dB/cm isolation and 13-dB/cm insertion loss, an integratable polarizer with 90-dB/cm rejection and about 0.8-dB/cm insertion loss, and a 300-m-long modulator requiring electric fields of 5 V m for 45% intensity modulation. In general, the resonant layer need not be epitaxial with the waveguide, allowing for integration with a variety of material systems.
The Floquet-Bloch theory is used to develop a theory for grating-assisted directional couplers wh... more The Floquet-Bloch theory is used to develop a theory for grating-assisted directional couplers which predicts the coupled power and coupling lengths and is applicable to lossy waveguides. This theory views grating-assisted directional couplers as conceptually similar to conventional synchronous (nongrating) couplers. In the Floquet-Bloch analysis of the directional coupler, it is necessary to include both proper and improper space harmonics. The determination of which space harmonics are improper is critical to the understanding of the coupler performance. The choice of the improper space harmonics used for the analysis of the coupler is different from that used in contemporary papers.
Floquet-Bloch theory is used to calculate the electromagnetic fields in a leakymode grating-assis... more Floquet-Bloch theory is used to calculate the electromagnetic fields in a leakymode grating-assisted directional coupler (LM-GADC) fabricated with semiconductor and glass materials. One waveguide is made from semiconductor materials (refractive index ≈ 3.2) while the second is made from glass (refractive index ≈ 1.45). The coupling of light between the two waveguides is assisted by a grating fabricated at the interface of the glass and semiconductor materials. Unlike typical GADC structures where power is exchanged between two waveguides using bound modes, this semiconductor/glass combination couples power between two waveguides using a bound mode (confined to the semiconductor) and a leaky mode (associated with the glass). The characteristics of the LM-GADC are discussed. Such LM-GADC couplers are expected to have numerous applications in areas such as laser-fiber coupling, photonic integrated circuits, and on-chip optical clock distribution. Analyses indicate that simple LM-GADCs can couple over 40 % of the optical power from one waveguide to another in distances less than 1.25 mm.
Resonant-layer effect (RLE) optical isolators can be integrated with a wide variety of optical wa... more Resonant-layer effect (RLE) optical isolators can be integrated with a wide variety of optical waveguide devices and systems and theoretically provide a high degree of isolation with low insertion loss. The effect of mode coupling within the isolator and the losses due to coupling between the isolator and the input and output waveguides on the performance of RLE isolators is calculated. The results predict that isolators integrated with semiconductor waveguides similar to those used for efficient lasers and amplifiers and isolators integrated with quartzlike waveguides can give 40dB of isolation with insertion losses below 3dB. The calculations also show relaxed dimensional tolerance and lengths in the 1–2mm range, which makes commercial production of such isolators attractive.
Four-port frustrated total internal reflection couplers in InP-based GaInAsP quantum-well substra... more Four-port frustrated total internal reflection couplers in InP-based GaInAsP quantum-well substrates are realized and characterized. Each coupler forms an " " at the perpendicular intersection of two ridge waveguides and is aligned 45 to the optical path. The 180-nm-wide couplers are fabricated by dry etching deep trenches through the quantum wells and backfilling with alumina () by atomic layer deposition. Coupling coefficients for the fabricated coupler are in good agreement with a three-dimensional finite-difference time-domain theory, and an 82% coupler efficiency is estimated.
A photonic true time delay cell with two waveguide couplers and five semiconductor optical amplif... more A photonic true time delay cell with two waveguide couplers and five semiconductor optical amplifiers is demonstrated. The five semiconductor optical amplifiers provide gain in the 1550-nm region and port selection to determine the time delay. With the amplifiers off the signal are blocked with extinction ratios of more than 10 dB. In the experiments reported here, the delay of 20 ns was provided by an optical fiber. Because of the potential for nanosecond switching times, the device has application in very agile phased array antenna applications, in optical switching and routing, and in optical filtering.
IEEE Journal of Selected Topics in Quantum Electronics, 2005
Semiconductor laser ridge arrays emitting 250 mW at a wavelength of 635 nm are designed for photo... more Semiconductor laser ridge arrays emitting 250 mW at a wavelength of 635 nm are designed for photodynamic therapy applications. Although ridge laser arrays are less efficient than broad area lasers, they are more reliable and can produce higher power from the same lateral width due to thermal considerations. An analytic expression for the active layer temperature of the laser array as a function of the ridge spacing, number of ridges and width is derived and has excellent agreement with a finite element analysis. This analytic expression allows optimization of the laser and the submount geometry to minimize the active region temperature with the constraint of a small submount, heatsink and package.
This paper presents an iterative model for the analysis of the current distribution in vertical-c... more This paper presents an iterative model for the analysis of the current distribution in vertical-cavity surface-emitting lasers (VCSELs) using a SPICE-like approach. The model includes a degeneracy correction for operation at and above threshold. The effect of the resistance due to the p-distributed Bragg reflector (p-DBR) mirror layers and the oxide layer on performance is investigated. Higher sheet resistance under the oxide layer reduces the threshold current, but reduces the current range over which single transverse mode operation occurs. The voltage drop across the p-DBR region dominates spatial hole burning, which is moderated by lateral drift and diffusion. This simple iterative model is applied to commercially available oxide-confined VCSELs.
The role of gain in an optical filter is advanced by good agreement between theory and experiment... more The role of gain in an optical filter is advanced by good agreement between theory and experiment presented herein. The particular integrated photonic filter is composed of four semiconductor optical amplifiers and one four-port coupler located at the intersection of the amplifiers. The four-port coupler is realized using frustrated total internal reflection off a very thin slab of alumina embedded in the substrate. The delta function response of the filter is measured using an ultra-fast laser and cross-correlator, and the measured transfer functions agree well with a z-transform-based description of the device.
An integrated photonic architecture is introduced and used to realize an optical filter with dire... more An integrated photonic architecture is introduced and used to realize an optical filter with direct form I realization. The architecture offers gain from semiconductor optical amplifiers, and this gain results in an active optical filter whose filter response depends on the individual gains. The presence of gain provides advantages in filter performance, and tunable and adaptive functionality. The optical filter is modeled as a discrete time system and the z-transform is used in its analysis and design. A low-pass filter design example is presented and the filter coefficients are derived in terms of gains and coupler splitting ratios. The region of stable operations is derived by applying the Schur-Cohn stability test.
A report is presented on distributed Bragg reflector lasers emitting in excess of 700 mW in a sin... more A report is presented on distributed Bragg reflector lasers emitting in excess of 700 mW in a single-spatial and single-spectral mode at 1065 nm. The threshold current of these devices is $30 mA, there is an L-I slope of 0.74 W=A, and a sidemode suppression ratio greater than 30 dB. The current and thermal tuning are 0.016 Å =mA and 0.7 Å = C, respectively.
A simple thin film effective index analysis for first-order gratings in Si photonic waveguides is... more A simple thin film effective index analysis for first-order gratings in Si photonic waveguides is shown to provide highly accurate results for reflected and transmitted power spectrums as long as the waveguide remains single mode and non-radiating. A cover layer can be added to the grating region of a Si photonic waveguide to increase the strength of the grating, modify transition losses from the input waveguide to the grating waveguide region, and/or modify the width of the reflectivity spectrum. For a given grating period, the peak reflection and spectral width of the reflectivity decrease as the duty cycle is decreased or increased from ~50%. For both radiating and multimode structures, the coupling between all modes, power radiated towards the superstrate (upwards), power radiated downwards (substrate) and transmitted power analyzed by Floquet-Bloch, Eigenmode Expansion and Finite Difference Time Domain methods show excellent agreement. Coupling coefficients calculated using an...
We show that in an optical waveguide with no material losses at wavelengths near the second-order... more We show that in an optical waveguide with no material losses at wavelengths near the second-order Bragg condition, there exists two pairs of modes. One pair has identical propagation constants but have different attenuation coefficients, while a second pair with identical propagation constants (different from the first pair) and have different attenuation coefficients. The four attenuation coefficients may have either a positive value, representing power leaking out of a waveguide mode or a negative value, representing power from an external source leaking into a mode. Moreover, a mode with a positive (negative) attenuation before the second Bragg condition, has a negative (positive) attenuation after the second Bragg condition. Radiation near the second-order Bragg condition of a periodic waveguide typically occurs at an angle perpendicular or nearly perpendicular to the propagation direction of the waveguide because the scattering centers have a period equal to or close to the per...
An equivalent surface current method is used to derive an analytic expression that approximates t... more An equivalent surface current method is used to derive an analytic expression that approximates the coupling coefficient, reflectivity bandwidth and group velocity for coupling between identical and non-identical TE modes in an asymmetric three-layer waveguide with a sinusoidal grating at one waveguide interface. The analytic expression for the coupling coefficient agrees with expressions derived by two other methods for contra-directional coupling between identical modes. The results from the analytical expressions are compared to results from a numerically accurate Floquet-Bloch solution. The analytical expressions, which do not depend on which interface contains the grating, provides almost identical results obtained by the accurate solution for shallow grating depths and small index changes at the grating interface, a case typical of single-mode distributed feedback lasers. However, the accurate numerical solution, unlike the analytic solution, shows that in waveguides with only a large index step at the grating interface, increasing the grating depth can result in decreasing the coupling coefficient, a case typical of some distributed Bragg reflector lasers. In highly confined silicon photonic waveguides (large index steps at both interfaces), the analytic expression gives accurate results even for deep gratings. The derivation of the analytical expression for the coupling coefficient in this paper using the equivalent surface current method extends the application of the previous analytic formulas to non-identical mode coupling where the forward and backward modes are not identical, which has application to gratings in multi-mode broadened waveguide lasers and amplifiers.
2016 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), 2016
The reflectivity of forty-grating sections consisting of two grating periods is simulated. Close ... more The reflectivity of forty-grating sections consisting of two grating periods is simulated. Close difference of two gratings periods causes similarity of the reflectivity of forty-gratings and single gratings except for the phase shift phenomenon.
The electro-optic switching properties of injection-coupled coherent twodimensional grating-surfa... more The electro-optic switching properties of injection-coupled coherent twodimensional grating-surface-emitting laser arrays with multiple gain sections and quantum well active layers are discussed and demonstrated. Within such an array of injection-coupled grating-surface-emitting lasers, a single gain section can be operated as intra-cavity saturable loss element that can modulate the output of the entire array. Experimental results demonstrate efficient sub-nanosecond switching of high-power grating-surface-emitting laser arrays by using only one gain section as an intra-cavity loss modulator.
Various types of surface-emitting semiconductor lasers are reviewed along with their anticipated ... more Various types of surface-emitting semiconductor lasers are reviewed along with their anticipated applications. The recent progress in grating-coupled surface-emitting (GSE) lasers is particularly emphasized. Such GSE arrays have operated continuously to more than 3 W and pulsed to more than 30 W. They have obtained cw threshold current densities of under 140 A/em 2 with cw differential quantum efficiencies of 20 to 40% per surface. Linewidths in the 40 MHz range have been obtained with output powers of 100 to 250 mW. The arrays typically consist of 10-30 mutually injection-coupled gain sections with l0 laterally coupled ridge-guided lasers in each gain section. A single GalnAs strained-layer quantum well with a graded index separate confinement heterostructure geometry allows junction down mounting with light emission through the transparent GaAs substrate. A surface relief grating is used for feedback and outcoupling.
Planar photonic integrated circuits based on four-port couplers offer enhanced sophistication and... more Planar photonic integrated circuits based on four-port couplers offer enhanced sophistication and functionality. Each four-port coupler is characterized by sixteen signal coupling coefficients governed by ten energy constraints. The ability to generate the constrained sixteen coupling coefficients is needed in the analysis of the four-port coupler. However, the energy constraint equations are nonlinear and cumbersome to solve directly. We introduce two techniques to reduce these signal coupling coefficients to a set of six free parameters. Hence we can characterize all possible couplers in terms of their sixteen constrained coupling coefficients, or either of two sets of six free parameters. This reduction in parameters has significant ramifications for the design, specification, and empirical characterization of these useful building blocks.
This paper investigates the effect of a high-refractiveindex layer added onto the clad layer of a... more This paper investigates the effect of a high-refractiveindex layer added onto the clad layer of an optical waveguide. With proper design, the value of the fundamental mode's confinement factor in the added layer can exhibit a resonance. This resonance depends on the added layer's location, thickness, complex index, and wavelength of operation. If loss is incorporated into this added layer, relatively small changes in waveguide properties can result in large changes in loss. This phenomenon is referred to in this paper as the resonant-layer effect (RLE). A number of devices, including isolators, polarizers, and modulators, can be made and/or improved by using the RLE. As examples, this paper describes an integratable isolator giving 240-dB/cm isolation and 13-dB/cm insertion loss, an integratable polarizer with 90-dB/cm rejection and about 0.8-dB/cm insertion loss, and a 300-m-long modulator requiring electric fields of 5 V m for 45% intensity modulation. In general, the resonant layer need not be epitaxial with the waveguide, allowing for integration with a variety of material systems.
The Floquet-Bloch theory is used to develop a theory for grating-assisted directional couplers wh... more The Floquet-Bloch theory is used to develop a theory for grating-assisted directional couplers which predicts the coupled power and coupling lengths and is applicable to lossy waveguides. This theory views grating-assisted directional couplers as conceptually similar to conventional synchronous (nongrating) couplers. In the Floquet-Bloch analysis of the directional coupler, it is necessary to include both proper and improper space harmonics. The determination of which space harmonics are improper is critical to the understanding of the coupler performance. The choice of the improper space harmonics used for the analysis of the coupler is different from that used in contemporary papers.
Floquet-Bloch theory is used to calculate the electromagnetic fields in a leakymode grating-assis... more Floquet-Bloch theory is used to calculate the electromagnetic fields in a leakymode grating-assisted directional coupler (LM-GADC) fabricated with semiconductor and glass materials. One waveguide is made from semiconductor materials (refractive index ≈ 3.2) while the second is made from glass (refractive index ≈ 1.45). The coupling of light between the two waveguides is assisted by a grating fabricated at the interface of the glass and semiconductor materials. Unlike typical GADC structures where power is exchanged between two waveguides using bound modes, this semiconductor/glass combination couples power between two waveguides using a bound mode (confined to the semiconductor) and a leaky mode (associated with the glass). The characteristics of the LM-GADC are discussed. Such LM-GADC couplers are expected to have numerous applications in areas such as laser-fiber coupling, photonic integrated circuits, and on-chip optical clock distribution. Analyses indicate that simple LM-GADCs can couple over 40 % of the optical power from one waveguide to another in distances less than 1.25 mm.
Resonant-layer effect (RLE) optical isolators can be integrated with a wide variety of optical wa... more Resonant-layer effect (RLE) optical isolators can be integrated with a wide variety of optical waveguide devices and systems and theoretically provide a high degree of isolation with low insertion loss. The effect of mode coupling within the isolator and the losses due to coupling between the isolator and the input and output waveguides on the performance of RLE isolators is calculated. The results predict that isolators integrated with semiconductor waveguides similar to those used for efficient lasers and amplifiers and isolators integrated with quartzlike waveguides can give 40dB of isolation with insertion losses below 3dB. The calculations also show relaxed dimensional tolerance and lengths in the 1–2mm range, which makes commercial production of such isolators attractive.
Four-port frustrated total internal reflection couplers in InP-based GaInAsP quantum-well substra... more Four-port frustrated total internal reflection couplers in InP-based GaInAsP quantum-well substrates are realized and characterized. Each coupler forms an " " at the perpendicular intersection of two ridge waveguides and is aligned 45 to the optical path. The 180-nm-wide couplers are fabricated by dry etching deep trenches through the quantum wells and backfilling with alumina () by atomic layer deposition. Coupling coefficients for the fabricated coupler are in good agreement with a three-dimensional finite-difference time-domain theory, and an 82% coupler efficiency is estimated.
A photonic true time delay cell with two waveguide couplers and five semiconductor optical amplif... more A photonic true time delay cell with two waveguide couplers and five semiconductor optical amplifiers is demonstrated. The five semiconductor optical amplifiers provide gain in the 1550-nm region and port selection to determine the time delay. With the amplifiers off the signal are blocked with extinction ratios of more than 10 dB. In the experiments reported here, the delay of 20 ns was provided by an optical fiber. Because of the potential for nanosecond switching times, the device has application in very agile phased array antenna applications, in optical switching and routing, and in optical filtering.
IEEE Journal of Selected Topics in Quantum Electronics, 2005
Semiconductor laser ridge arrays emitting 250 mW at a wavelength of 635 nm are designed for photo... more Semiconductor laser ridge arrays emitting 250 mW at a wavelength of 635 nm are designed for photodynamic therapy applications. Although ridge laser arrays are less efficient than broad area lasers, they are more reliable and can produce higher power from the same lateral width due to thermal considerations. An analytic expression for the active layer temperature of the laser array as a function of the ridge spacing, number of ridges and width is derived and has excellent agreement with a finite element analysis. This analytic expression allows optimization of the laser and the submount geometry to minimize the active region temperature with the constraint of a small submount, heatsink and package.
This paper presents an iterative model for the analysis of the current distribution in vertical-c... more This paper presents an iterative model for the analysis of the current distribution in vertical-cavity surface-emitting lasers (VCSELs) using a SPICE-like approach. The model includes a degeneracy correction for operation at and above threshold. The effect of the resistance due to the p-distributed Bragg reflector (p-DBR) mirror layers and the oxide layer on performance is investigated. Higher sheet resistance under the oxide layer reduces the threshold current, but reduces the current range over which single transverse mode operation occurs. The voltage drop across the p-DBR region dominates spatial hole burning, which is moderated by lateral drift and diffusion. This simple iterative model is applied to commercially available oxide-confined VCSELs.
The role of gain in an optical filter is advanced by good agreement between theory and experiment... more The role of gain in an optical filter is advanced by good agreement between theory and experiment presented herein. The particular integrated photonic filter is composed of four semiconductor optical amplifiers and one four-port coupler located at the intersection of the amplifiers. The four-port coupler is realized using frustrated total internal reflection off a very thin slab of alumina embedded in the substrate. The delta function response of the filter is measured using an ultra-fast laser and cross-correlator, and the measured transfer functions agree well with a z-transform-based description of the device.
An integrated photonic architecture is introduced and used to realize an optical filter with dire... more An integrated photonic architecture is introduced and used to realize an optical filter with direct form I realization. The architecture offers gain from semiconductor optical amplifiers, and this gain results in an active optical filter whose filter response depends on the individual gains. The presence of gain provides advantages in filter performance, and tunable and adaptive functionality. The optical filter is modeled as a discrete time system and the z-transform is used in its analysis and design. A low-pass filter design example is presented and the filter coefficients are derived in terms of gains and coupler splitting ratios. The region of stable operations is derived by applying the Schur-Cohn stability test.
A report is presented on distributed Bragg reflector lasers emitting in excess of 700 mW in a sin... more A report is presented on distributed Bragg reflector lasers emitting in excess of 700 mW in a single-spatial and single-spectral mode at 1065 nm. The threshold current of these devices is $30 mA, there is an L-I slope of 0.74 W=A, and a sidemode suppression ratio greater than 30 dB. The current and thermal tuning are 0.016 Å =mA and 0.7 Å = C, respectively.
SURFACE EMITTING SEMICONDUCTOR LASERS AND ARRAYS, 1993
Practical demonstrations of diode laser emission from the broad surface area rather than from the... more Practical demonstrations of diode laser emission from the broad surface area rather than from the cleaved facet of the wafer are relatively recent. This is so despite the fact that the concepts are many years old. The vertical-cavity approach was demonstrated by Melngailis in 1964, and the grating surface emitting and folded-cavity approach were reported by many authors in the mid to late 1970s. Many, perhaps most, of the concepts discussed in this book were around for many years before they were actively pursued. The advances over the last ten years, mainly in materials, are largely responsible for the capability to implement the ideas presented into working devices. We can look forward to continued progress in materials, processing, and design during the next decade and can expect to see semiconductor laser performance outstripping even our present dreams. There are now frequent reports on all three principal types of diode laser and diode laser array surface emitters in the literature. Unlike edge-emitting semiconductor lasers, the surface emission approach allows the use of mass production techniques throughout the fabrication process. In addition, the surface emission approach allows testing of the completed devices at the wafer level, before dicing and packaging. These same capabilities yielded tremendous reductions in cost and enormous increases in the performance and reliability of transistors and other solid state electronic devices. Surface-emitting approaches also allow the integration of single or numerous lasers to form photonic integrated circuits or high power, monolithic, two-dimensional arrays. Because of the now extensive literature on surface-emitting diode lasers and arrays and the proposed and emerging applications of these exciting and practical new devices in a variety of systems, we feel that this in-depth book covering the field will be useful to researchers, users, and students interested in the field of lasers, electrooptics, and optical communication. Recent work has been motivated by numerous goals, including low power, integrated sources to replace electrical interconnects with optical interconnects for ultra large-scale integrated circuits; two-dimensional, independently addressable laser arrays for neural networks; steerable output beams for optical computers; high power with large emitting areas for pumping solid-state lasers; and coherent, single frequency, high-power operation with a controlled output beam for space communication and second harmonic generation. The information in this book is intended to provide the reader with both knowledge about fundamental concepts and the present state of the art of surface-emitting lasers. There are definitive chapters on vertical-cavity, etched facet-mirror, and grating surface emitters. Additional chapters treat the operation of Bragg grating couplers; edge-emitting diode laser arrays; the theory of phase locking, modes, and beam steering of surface-emitting arrays; external methods of phase locking arrays; coherence and phase control in laser arrays; and thermal considerations in two-dimensional surface-emitting arrays. We have fortunately been able to enlist some of the leading researchers and developers of surface-emitting diode lasers to contribute to this book. We wish to thank them for many interesting and productive discussions in connection with the preparation of this work. We also wish· to thank RCA Laboratories (now the David Sarnoff Research Center), Princeton, New Jersey, for providing both of us with talented collaborators, up-to-date equipment, and a pleasant environment in which most of our work described herein was carried out.
Uploads
Papers by Gary Evans
There are now frequent reports on all three principal types of diode laser
and diode laser array surface emitters in the literature. Unlike edge-emitting
semiconductor lasers, the surface emission approach allows the use of mass production techniques throughout the fabrication process. In addition, the surface emission approach allows testing of the completed devices at the wafer level, before dicing and packaging. These same capabilities yielded tremendous reductions in cost and enormous increases in the performance and reliability of transistors and other solid state electronic devices. Surface-emitting approaches also allow the integration of single or numerous lasers to form photonic integrated circuits or high power, monolithic, two-dimensional arrays.
Because of the now extensive literature on surface-emitting diode lasers
and arrays and the proposed and emerging applications of these exciting and
practical new devices in a variety of systems, we feel that this in-depth book
covering the field will be useful to researchers, users, and students interested in the field of lasers, electrooptics, and optical communication. Recent work has been motivated by numerous goals, including low power, integrated sources to replace electrical interconnects with optical interconnects for ultra large-scale integrated circuits; two-dimensional, independently addressable laser arrays for neural networks; steerable output beams for optical computers; high power with large emitting areas for pumping solid-state lasers; and coherent, single frequency, high-power operation with a controlled output beam for space communication and second harmonic generation.
The information in this book is intended to provide the reader with both
knowledge about fundamental concepts and the present state of the art of surface-emitting lasers. There are definitive chapters on vertical-cavity, etched facet-mirror, and grating surface emitters. Additional chapters treat the operation of Bragg grating couplers; edge-emitting diode laser arrays; the theory of phase locking, modes, and beam steering of surface-emitting arrays; external methods of phase locking arrays; coherence and phase control in laser arrays; and thermal considerations in two-dimensional surface-emitting arrays.
We have fortunately been able to enlist some of the leading researchers and
developers of surface-emitting diode lasers to contribute to this book. We wish to thank them for many interesting and productive discussions in connection with the preparation of this work. We also wish· to thank RCA Laboratories (now the David Sarnoff Research Center), Princeton, New Jersey, for providing both of us with talented collaborators, up-to-date equipment, and a pleasant environment in which most of our work described herein was carried out.