We review laser diode feedback interferometry as a general tool for sensing applications. After o... more We review laser diode feedback interferometry as a general tool for sensing applications. After outlining the basic principles and the theoretical approaches used to describe the phenomenon, we present a few selected examples of applications in interferometry, as developed by various groups in recent years, such as a displacement sensor, a velocimeter or vibration sensor, and an absolute distance meter or range finder and angle sensor. Experimental results are also reported as an illustration.
We demonstrate an easy-to-implement method to determine the linewidth of a laser diode based on t... more We demonstrate an easy-to-implement method to determine the linewidth of a laser diode based on the measurement of phase noise in a self-mixing interferometer. The method features a self-aligned experimental setup with an overall length much shorter than the laser coherence length; the method does not require rf measurements and gives results in agreement with the selfheterodyne technique.
We analyze the ultimate timing precision of schemes for time-of-flight measurements with rangefin... more We analyze the ultimate timing precision of schemes for time-of-flight measurements with rangefinders and LiDARs, based on short-pulse, sine-wave modulated, and long-pulse techniques, and consider both random and systematic contributions to the total error. When quantum noise of detected photons prevails, the random error is given by a characteristic time of the waveform divided by the square root of detected photons. When the detector is thermal-noise limited, the random error is increased by the square root of the ratio thermal-equivalent power to detected power. The systematic error may become much larger than the random one, but an appropriate choice of parameters can reduce it below the random error.
We develop a self-mixing interferometer capable of measuring the position (with half-wavelength r... more We develop a self-mixing interferometer capable of measuring the position (with half-wavelength resolution) and the two attitude angles - pitch and yaw - (with 15 microrad resolution) of a machine tool turret. The three measurements are performed, for the first time to the best of our knowledge, simultaneously and using a single channel optical signal.
We demonstrate that the native configuration of a self-mixing interferometer attains a minimum de... more We demonstrate that the native configuration of a self-mixing interferometer attains a minimum detectable displacement of 0.72 nm or λ / 1870 at the laser wavelength of 1310 nm, obtained by the bare laser diode package including a monitor photodiode, observed in the electrical domain by means of an oscilloscope and without any electronic processing of the signal.
Using a glass-clad Ti:sapphire crystal fiber (CF) as the gain medium, we demonstrate for the firs... more Using a glass-clad Ti:sapphire crystal fiber (CF) as the gain medium, we demonstrate for the first time a diodepumped, 25-mW tunable laser with a 180-nm tuning range. Active medium is a 2.4-cm long, a-cut Ti:sapphire CF we have drawn with an elliptical core of 13-μm diameter in the [0001] axis and 15.5-μm diameter in the [1100] axis. The CF is cladded with silica and has high efficiency (88%) of coupling to the pump, a diode laser emitting 1-W at 520-nm. A blazed grating provides a continuous smooth tuning on the wavelength range from 700 to 880 nm.
We present a new optical instrument for vibrations measurement, based on a method to read the fre... more We present a new optical instrument for vibrations measurement, based on a method to read the frequency modulation of a laser diode self-mixing interferometer. The laser source, when exposed to back-injection of its emitted power, is perturbed in frequency and amplitude (self-mixing effect). When the optical back-injection level is low, the self-mixing effect introduces a frequency and amplitude modulation (FM and AM) of the emitted optical field. We demonstrated with a prototype instrument that the performances of FM modulation, in terms of resolution, sensitivity and bandwidth, show an improvement of two order of magnitude with respect to well-known AM self-mixing interferometer.
This study numerically investigates the enhancement of photonic microwave generation using an opt... more This study numerically investigates the enhancement of photonic microwave generation using an optically injected semiconductor laser operating at period-one (P1) nonlinear dynamics through ultrashort optical feedback. For the purpose of practical applications where system miniaturization is generally preferred, a feedback delay time that is one to two orders of magnitude shorter than the relaxation resonance period of a typical laser is emphasized. Various dynamical states that are more complicated than the P1 dynamics can be excited under a number of ultrashort optical feedback conditions. Within the range of the P1 dynamics, on one hand, the frequency of the P1 microwave oscillation can be greatly enhanced by up to more than three folds. Generally speaking, the microwave frequency enhances with the optical feedback power and phase, while it varies saw-wise with the optical feedback delay time. On the other hand, the purity of the P1 microwave oscillation can be highly improved by ...
We present a new concept to implement phase modulation in DQPSK transmitter: moving the physical ... more We present a new concept to implement phase modulation in DQPSK transmitter: moving the physical phase modulator from outside the laser cavity where it is usually placed, to inside the cavity. On analysing the new scheme, we find that the in-cavity process of phase-frequency-phase conversion provides a phase gain, which is larger than one up to bit-frequency of about 100 GHz. We supplement the first-hand calculations by numerical simulations based on a travelling-wave model of the field internal to the cavity and find good agreement with theory.
In a self-mixing interferometer based on a diode laser, the measurement of the external reflector... more In a self-mixing interferometer based on a diode laser, the measurement of the external reflector displacement s(t) is carried out by looking at the optical-phase signal cos 2ks(t), a signal readily detected as an amplitude modulation (AM) of emitted power. In contrast, the other available signal, sin2ks(t), a frequency modulation (FM) of the emitted field at optical frequency, is never used because difficult to recover. Recently, Contreras et al. used a narrow-band acetylene cell to convert the FM into an amplitude signal, finding it is larger and has a better SNR than the AM. In this paper, we analyze the advantages of the new CFM (converted-FM) signal, calculating both amplitude and SNR, and compare theoretical results to published experimental evidence, finding good agreement. We then present options for realizing the selective filter in different configurations and technology. Finally, we evaluate the improvement offered by CFM in a number of measurements, like sub-wavelength vibrations, digital readout displacement, and diode laser alpha factor.
It is well known that back-reflections in single mode semiconductor lasers usually lead to line b... more It is well known that back-reflections in single mode semiconductor lasers usually lead to line broadening and amplitude increase of noise. We will show that a particular choice of the laser bias, which we have called the crossover working point, is helpful to mitigate these effects. Starting the analysis using a self-mixing interferometer, we demonstrate a decrease of the disturbances as high as 40dB in the weak and moderate feedback regimes. We also extend the analysis for incoherent and coherent feedback for the case of high level of injection arising from an all-fiber setup. Two different semiconductor laser devices have been tested to verify the analysis predictions, with good agreement with experimental results.
2013 International Conference on Advanced Optoelectronics and Lasers (CAOL 2013), 2013
We outline the fundamentals of optical cryptography with coupled semiconductor lasers, and the as... more We outline the fundamentals of optical cryptography with coupled semiconductor lasers, and the associated tools of optical chaos generation and synchronization, as well as chaos coding of transmitted information, with special reference to CM (Chaos masking) and CSK (Chaos Shift Keying). We present different versions of such schemes which have been numerically and/or experimentally tested both with discrete component crypto-systems and with a PIC (Photonic Integrated Circuit) realization of the chaotic source. Finally, we outline some recent developments on the chaos secure transmission technique.
ABSTRACT High-performance baffles are required in the operation of space sensors mounted aboard a... more ABSTRACT High-performance baffles are required in the operation of space sensors mounted aboard a satellite to track stars for attitude control or to identify the sky region aimed by a paralleled X-ray telescope. For example, on a typical X-ray observation mission, the star sensor shall identify stars in a 8 deg by 8 deg field of view down to the 6th magnitude, even when very bright sources (as the sun or the earth horizon) are only 10-15 degrees off the field of view. This corresponds to attenuate stray light down to approximately 10-9, what calls for a very sophisticated design of the optical baffle and also is an unusual requirement for the measurement of attenuation in the test-laboratory to validate the baffle before launch.1,2.
Effects of optical feedback on period-one nonlinear dynamics of an optically injected semiconduct... more Effects of optical feedback on period-one nonlinear dynamics of an optically injected semiconductor laser are numerically investigated. The optical feedback can suppress the period-one dynamics and excite other more complex dynamics if the feedback level is high except for extremely short feedback delay times. Within the range of the period-one dynamics, however, the optical feedback can stabilize the period-one dynamics in such a manner that significant reduction of microwave linewidth and phase noise is achieved, up to more than two orders of magnitude. A high feedback level and/or a long feedback delay time are generally preferred for such microwave stabilization. However, considerably enhanced microwave linewidth and phase noise happen periodically at certain feedback delay times, which is strongly related to the behavior of locking between the period-one microwave oscillation and the feedback loop modes. The extent of these enhancements reduces if the feedback level is high. Wh...
The spectral dependence of the gain and noise figure of a 1.55 mm semiconductor optical amplifier... more The spectral dependence of the gain and noise figure of a 1.55 mm semiconductor optical amplifier (SOA) in linear and saturated operation is calculated using an accurate description of the population inversion factor n sp using a detailed density-matrix gain model, and taking longitudinal nonuniformity of carrier density into account by properly sectioning the device. Results show that the lowest noise figure is always attained at a wavelength longer than the gain peak, and that the À3 dB gain bandwidth increases in saturated operation. The performance of a SOA-based 4 Â 4 InP switch matrix is analysed. When the matrix is in the 'on' state, it is equivalent to a cascade of three SOAs, which are analysed using longitudinal sectioning of each device, and by taking into account the amplified spontaneous emission (ASE) propagating forward and backward within the matrix. The influence of input=output passive splitter loss on the spectral noise figure of the matrix is also assessed.
Noise in 1550 nm gain-clamped and conventional SOAs is studied using a detailed device model. By ... more Noise in 1550 nm gain-clamped and conventional SOAs is studied using a detailed device model. By dividing the amplifier in M longitudinal sections were are able to account for longitudinal non-uniformity of the carrier density. We use a rate equation for locally averaged values of carriers and photons density for each section, obtaining a highly non- uniform spatial profile of
We review laser diode feedback interferometry as a general tool for sensing applications. After o... more We review laser diode feedback interferometry as a general tool for sensing applications. After outlining the basic principles and the theoretical approaches used to describe the phenomenon, we present a few selected examples of applications in interferometry, as developed by various groups in recent years, such as a displacement sensor, a velocimeter or vibration sensor, and an absolute distance meter or range finder and angle sensor. Experimental results are also reported as an illustration.
We demonstrate an easy-to-implement method to determine the linewidth of a laser diode based on t... more We demonstrate an easy-to-implement method to determine the linewidth of a laser diode based on the measurement of phase noise in a self-mixing interferometer. The method features a self-aligned experimental setup with an overall length much shorter than the laser coherence length; the method does not require rf measurements and gives results in agreement with the selfheterodyne technique.
We analyze the ultimate timing precision of schemes for time-of-flight measurements with rangefin... more We analyze the ultimate timing precision of schemes for time-of-flight measurements with rangefinders and LiDARs, based on short-pulse, sine-wave modulated, and long-pulse techniques, and consider both random and systematic contributions to the total error. When quantum noise of detected photons prevails, the random error is given by a characteristic time of the waveform divided by the square root of detected photons. When the detector is thermal-noise limited, the random error is increased by the square root of the ratio thermal-equivalent power to detected power. The systematic error may become much larger than the random one, but an appropriate choice of parameters can reduce it below the random error.
We develop a self-mixing interferometer capable of measuring the position (with half-wavelength r... more We develop a self-mixing interferometer capable of measuring the position (with half-wavelength resolution) and the two attitude angles - pitch and yaw - (with 15 microrad resolution) of a machine tool turret. The three measurements are performed, for the first time to the best of our knowledge, simultaneously and using a single channel optical signal.
We demonstrate that the native configuration of a self-mixing interferometer attains a minimum de... more We demonstrate that the native configuration of a self-mixing interferometer attains a minimum detectable displacement of 0.72 nm or λ / 1870 at the laser wavelength of 1310 nm, obtained by the bare laser diode package including a monitor photodiode, observed in the electrical domain by means of an oscilloscope and without any electronic processing of the signal.
Using a glass-clad Ti:sapphire crystal fiber (CF) as the gain medium, we demonstrate for the firs... more Using a glass-clad Ti:sapphire crystal fiber (CF) as the gain medium, we demonstrate for the first time a diodepumped, 25-mW tunable laser with a 180-nm tuning range. Active medium is a 2.4-cm long, a-cut Ti:sapphire CF we have drawn with an elliptical core of 13-μm diameter in the [0001] axis and 15.5-μm diameter in the [1100] axis. The CF is cladded with silica and has high efficiency (88%) of coupling to the pump, a diode laser emitting 1-W at 520-nm. A blazed grating provides a continuous smooth tuning on the wavelength range from 700 to 880 nm.
We present a new optical instrument for vibrations measurement, based on a method to read the fre... more We present a new optical instrument for vibrations measurement, based on a method to read the frequency modulation of a laser diode self-mixing interferometer. The laser source, when exposed to back-injection of its emitted power, is perturbed in frequency and amplitude (self-mixing effect). When the optical back-injection level is low, the self-mixing effect introduces a frequency and amplitude modulation (FM and AM) of the emitted optical field. We demonstrated with a prototype instrument that the performances of FM modulation, in terms of resolution, sensitivity and bandwidth, show an improvement of two order of magnitude with respect to well-known AM self-mixing interferometer.
This study numerically investigates the enhancement of photonic microwave generation using an opt... more This study numerically investigates the enhancement of photonic microwave generation using an optically injected semiconductor laser operating at period-one (P1) nonlinear dynamics through ultrashort optical feedback. For the purpose of practical applications where system miniaturization is generally preferred, a feedback delay time that is one to two orders of magnitude shorter than the relaxation resonance period of a typical laser is emphasized. Various dynamical states that are more complicated than the P1 dynamics can be excited under a number of ultrashort optical feedback conditions. Within the range of the P1 dynamics, on one hand, the frequency of the P1 microwave oscillation can be greatly enhanced by up to more than three folds. Generally speaking, the microwave frequency enhances with the optical feedback power and phase, while it varies saw-wise with the optical feedback delay time. On the other hand, the purity of the P1 microwave oscillation can be highly improved by ...
We present a new concept to implement phase modulation in DQPSK transmitter: moving the physical ... more We present a new concept to implement phase modulation in DQPSK transmitter: moving the physical phase modulator from outside the laser cavity where it is usually placed, to inside the cavity. On analysing the new scheme, we find that the in-cavity process of phase-frequency-phase conversion provides a phase gain, which is larger than one up to bit-frequency of about 100 GHz. We supplement the first-hand calculations by numerical simulations based on a travelling-wave model of the field internal to the cavity and find good agreement with theory.
In a self-mixing interferometer based on a diode laser, the measurement of the external reflector... more In a self-mixing interferometer based on a diode laser, the measurement of the external reflector displacement s(t) is carried out by looking at the optical-phase signal cos 2ks(t), a signal readily detected as an amplitude modulation (AM) of emitted power. In contrast, the other available signal, sin2ks(t), a frequency modulation (FM) of the emitted field at optical frequency, is never used because difficult to recover. Recently, Contreras et al. used a narrow-band acetylene cell to convert the FM into an amplitude signal, finding it is larger and has a better SNR than the AM. In this paper, we analyze the advantages of the new CFM (converted-FM) signal, calculating both amplitude and SNR, and compare theoretical results to published experimental evidence, finding good agreement. We then present options for realizing the selective filter in different configurations and technology. Finally, we evaluate the improvement offered by CFM in a number of measurements, like sub-wavelength vibrations, digital readout displacement, and diode laser alpha factor.
It is well known that back-reflections in single mode semiconductor lasers usually lead to line b... more It is well known that back-reflections in single mode semiconductor lasers usually lead to line broadening and amplitude increase of noise. We will show that a particular choice of the laser bias, which we have called the crossover working point, is helpful to mitigate these effects. Starting the analysis using a self-mixing interferometer, we demonstrate a decrease of the disturbances as high as 40dB in the weak and moderate feedback regimes. We also extend the analysis for incoherent and coherent feedback for the case of high level of injection arising from an all-fiber setup. Two different semiconductor laser devices have been tested to verify the analysis predictions, with good agreement with experimental results.
2013 International Conference on Advanced Optoelectronics and Lasers (CAOL 2013), 2013
We outline the fundamentals of optical cryptography with coupled semiconductor lasers, and the as... more We outline the fundamentals of optical cryptography with coupled semiconductor lasers, and the associated tools of optical chaos generation and synchronization, as well as chaos coding of transmitted information, with special reference to CM (Chaos masking) and CSK (Chaos Shift Keying). We present different versions of such schemes which have been numerically and/or experimentally tested both with discrete component crypto-systems and with a PIC (Photonic Integrated Circuit) realization of the chaotic source. Finally, we outline some recent developments on the chaos secure transmission technique.
ABSTRACT High-performance baffles are required in the operation of space sensors mounted aboard a... more ABSTRACT High-performance baffles are required in the operation of space sensors mounted aboard a satellite to track stars for attitude control or to identify the sky region aimed by a paralleled X-ray telescope. For example, on a typical X-ray observation mission, the star sensor shall identify stars in a 8 deg by 8 deg field of view down to the 6th magnitude, even when very bright sources (as the sun or the earth horizon) are only 10-15 degrees off the field of view. This corresponds to attenuate stray light down to approximately 10-9, what calls for a very sophisticated design of the optical baffle and also is an unusual requirement for the measurement of attenuation in the test-laboratory to validate the baffle before launch.1,2.
Effects of optical feedback on period-one nonlinear dynamics of an optically injected semiconduct... more Effects of optical feedback on period-one nonlinear dynamics of an optically injected semiconductor laser are numerically investigated. The optical feedback can suppress the period-one dynamics and excite other more complex dynamics if the feedback level is high except for extremely short feedback delay times. Within the range of the period-one dynamics, however, the optical feedback can stabilize the period-one dynamics in such a manner that significant reduction of microwave linewidth and phase noise is achieved, up to more than two orders of magnitude. A high feedback level and/or a long feedback delay time are generally preferred for such microwave stabilization. However, considerably enhanced microwave linewidth and phase noise happen periodically at certain feedback delay times, which is strongly related to the behavior of locking between the period-one microwave oscillation and the feedback loop modes. The extent of these enhancements reduces if the feedback level is high. Wh...
The spectral dependence of the gain and noise figure of a 1.55 mm semiconductor optical amplifier... more The spectral dependence of the gain and noise figure of a 1.55 mm semiconductor optical amplifier (SOA) in linear and saturated operation is calculated using an accurate description of the population inversion factor n sp using a detailed density-matrix gain model, and taking longitudinal nonuniformity of carrier density into account by properly sectioning the device. Results show that the lowest noise figure is always attained at a wavelength longer than the gain peak, and that the À3 dB gain bandwidth increases in saturated operation. The performance of a SOA-based 4 Â 4 InP switch matrix is analysed. When the matrix is in the 'on' state, it is equivalent to a cascade of three SOAs, which are analysed using longitudinal sectioning of each device, and by taking into account the amplified spontaneous emission (ASE) propagating forward and backward within the matrix. The influence of input=output passive splitter loss on the spectral noise figure of the matrix is also assessed.
Noise in 1550 nm gain-clamped and conventional SOAs is studied using a detailed device model. By ... more Noise in 1550 nm gain-clamped and conventional SOAs is studied using a detailed device model. By dividing the amplifier in M longitudinal sections were are able to account for longitudinal non-uniformity of the carrier density. We use a rate equation for locally averaged values of carriers and photons density for each section, obtaining a highly non- uniform spatial profile of
Uploads
Papers by Donati Silvano