Papers by Rostislav Roussev
We demonstrate an optically controlled, continuously-tunable dispersionless optical delay element... more We demonstrate an optically controlled, continuously-tunable dispersionless optical delay element using a two-pump PPLN waveguide, dispersion compensated fiber and a dispersion compensator. A Continuous optical delay up to 44-ns is shown for 10-Gb/s NRZ applications.
Four User Spectrally Coded O-CDMA System Demonstration at 2.5 Gb/s Using Low Power Nonlinear Processing
Optical code-division multiple-access (O-CDMA) is receiving increasing attention due to its poten... more Optical code-division multiple-access (O-CDMA) is receiving increasing attention due to its potential for enhanced information security, simplified and decentralized network control, and increased flexibility in the granularity of bandwidth that can be provisioned. In O-CDMA, different users whose signals may be overlapped both in time and frequency share a common communications medium; multipleaccess is achieved by assigning different, minimally interfering code sequences to different CDMA transmitters. In many O-CDMA approaches, input ultrashort pulses are time-spread during the encoding process into lower intensity noise-like signals [1-2]. In the receiver, data corresponding to a desired user is separated from multi-access interference via a matched filtering (decoding) operation, in which properly decoded signals are converted back to the original pulse-like signals, while improperly decoded signals remain low-intensity noise-like temporally broad waveforms. Since the energy in properly and improperly decoded signals is similar, and since the temporal duration of even improperly decoded signals is on the order of the bit period or below, both properly and improperly decoded signals will appear identical to an electronic receiver band-limited to the data rate. Consequently either very fast electronics or a nonlinear optical intensity discriminator play a critical role in separating properly decoded short pulses from improperly decoded multi-access interference.
Highly efficient SHG using non-critical quasi-phase matching for the TM/sub 01/ -mode in annealed proton-exchange waveguides in 5% MgO-doped LiNbO/sub 3/
Conference on Lasers and Electro-Optics, Jun 6, 2003
Non-critical phase-matching is obtained for higher-order mode second harmonic generation free fro... more Non-critical phase-matching is obtained for higher-order mode second harmonic generation free from photorefractive damage. Conversion efficiency of 780 %/W was measured during frequency doubling of 1548 nm in a 4.5 cm long waveguide.
15th International Conference on Ultrafast Phenomena, 2006
We retrieve intensity and phase profiles of few hundred femtosecond optical pulses at 6 nW averag... more We retrieve intensity and phase profiles of few hundred femtosecond optical pulses at 6 nW average power via second-harmonic generation FROG using a new fiber-pigtailed aperiodically poled lithium niobate waveguide with apodized design.
Optics Letters, Feb 1, 2002
Efficient three-wave mixing devices have numerous applications, including wavelength conversion, ... more Efficient three-wave mixing devices have numerous applications, including wavelength conversion, dispersion compensation, and all-optical switching. Second-harmonic generation (SHG) is a useful diagnostic for neardegenerate operation of these devices. With buried waveguides formed in periodically poled lithium niobate by annealed and reverse proton exchange, we demonstrate what is believed to be the highest normalized conversion efficiency ͑150%͞W cm 2 ͒ for SHG in the 1550-nm communications band reported to date.
Conference on Lasers and Electro-Optics, May 16, 2004
We demonstrate ultrafast O-CDMA nonlinear waveform discrimination at 10 GHz with less than 1 mW c... more We demonstrate ultrafast O-CDMA nonlinear waveform discrimination at 10 GHz with less than 1 mW coupled into a nonlinear PPLN waveguide and greater than 20 dB contrast ratio between coded and uncoded waveforms.
Fully dispersion compensated /spl sim/500 fs pulse transmission over 50 km SMF and application to ultrafast O-CDMA
We demonstrate essentially distortionless 50 km fiber transmission for -500 fs pulses using dispe... more We demonstrate essentially distortionless 50 km fiber transmission for -500 fs pulses using dispersion compensating fiber and a programmable pulse shaper as a spectral phase equalizer. Application in ultrafast O-CDMA system experiments is demonstrated.
Low power 4x10 Gb/s O-CDMA system using a double Hadamard code based spectral phase correlator
ABSTRACT
Soliton-controlled switching in photorefractive media
Journal of Modern Optics, Jun 1, 1997
Page 1. JOURNAL OF MODERN OPTICS, 1997, VOL. 44, NO. 6, 1127-1140 Soliton-controlled switching in... more Page 1. JOURNAL OF MODERN OPTICS, 1997, VOL. 44, NO. 6, 1127-1140 Soliton-controlled switching in photorefractive media ED EUGENIEVA, RV ROUSSEV and SG DINEV Sofia University, Department of Physics, 5, J. Bourchier Blvd., BG-1164 Sofia, Bulgaria ...
/spl lambda/-Tripler based on periodically poled lithium niobate
Conference on Lasers and Electro-Optics, 2003. CLEO '03., 2003
We present experimental results on a 1 -Tripler based on Optical Parametric Oscillation and Diffe... more We present experimental results on a 1 -Tripler based on Optical Parametric Oscillation and Difference Frequency Generation in a monolithic Periodically Poled Lithium Niobate(PPLN) device. 51% photon-conversion efficiency and 2 . 6 ~ enhancement in the OPO idler output is demonstrated. 02003 Optical Society of America OCIS codes. (190.4970) Parametric oscillators and amplifiers ; (190.2620) Frequency conversion Coherent sources of mid-IR radiation (3 pm ) have applications for detection of gases using CRDLAS[l]. They can also pump ZGP based OPOs to yield tunable 6-8 pm radiation for measuring the vapor phase spectra of explosives[2] and OP-GaAs OPAs with wide bandwidth ( > 1 octave, between 5-10 pm)[3]. Here, we present an approach to efficiently generate 3.192 pm radiation based on a monolitluc PPLN A-tripler device in a resonant OPOiDFG configurntion pumped at 1.064 pm. A simple OPO where AI = 3 h , suffers from a quantum defect of 3. DFG of the resonant signal and non-resonant...
Spatial optical solitons in Reverse Proton Exchanged PPLN waveguides
Nonlinear Guided Waves and Their Applications, 2004
Abstract: Low-threshold spatial optical solitons are observed for the first time in buried planar... more Abstract: Low-threshold spatial optical solitons are observed for the first time in buried planar waveguides obtained by reverse-proton-exchanged periodically poled LiNbO3. ... Buried channel waveguides fabricated by reverse proton exchange (RPE) in Periodically-Poled Lithium ...
λ-Tripler based on periodically poled lithium niobate
<title>Vapor transport equilibrated lithium niobate resistant to photorefractive damage</title>
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications IV, 2005
ABSTRACT We use a combination of vapor transport equilibration and moderate MgO doping (&lt;=... more ABSTRACT We use a combination of vapor transport equilibration and moderate MgO doping (&lt;= 1%) to explore near-stoichiometric damage resistant lithium niobate crystals with improved properties for periodic poling and annealed-proton-exchange waveguide fabrication compared to the commercially available 5-mol % MgO-doped crystals. High C C C, damage resistance, measured by the saturated space-charge field generated in the crystal by 514 nm radiation, was obtained for all MgO doping concentrations (0.3, 0.5 and 1%) with appropriate equilibration. Green-induced infrared absorption was also measured in the 0.3-% doped crystal and was below the detection limit. Dispersion in the region 460-1550 nm was measured. Periodic poling was performed using LiCl solution electrodes. Poling quality improves with lowering MgO concentration. Waveguides for frequency doubling of 1550 nm were fabricated in the 1% doped crystal with losses as low as 0.4 dB/cm and normalized efficiency of similar to 10 %/Wcm(2).
All-Optical Wavelength Conversion in MgO:LiNbO3 and LiNbO3: A study of Photorefraction
Advanced Solid-State Lasers, 2002
... RG Batchko, T. Alfrey, R. Roussev, MH Sher, SS Kirn, LR Marshall Lightbit Corporation 411 Cly... more ... RG Batchko, T. Alfrey, R. Roussev, MH Sher, SS Kirn, LR Marshall Lightbit Corporation 411 Clyde Avenue, Mountain View, CA 94043 ... substrates using the conventional method of photolithographically-defined electric-field poling [3]. Domain grating periods of 14.7 jim in PPLN ...
Digest of the LEOS Summer Topical Meetings, 2005.
This talk discusses examples of our work on linear optical signal processing using pulse shapers ... more This talk discusses examples of our work on linear optical signal processing using pulse shapers (O-CDMA encoding and dispersion compensation) and low power nonlinear processing using PPLN waveguides (O-CDMA waveform discrimination and ultrashort pulse measurement).
Wavelength-Switched Optical Systems
Optics Letters, 2007
We demonstrate full characterization of femtosecond pulse distortion induced by all-order polariz... more We demonstrate full characterization of femtosecond pulse distortion induced by all-order polarization mode dispersion (PMD) at selected polarization states via second-harmonic generation (SHG) frequency-resolved optical gating (FROG) measurements at an average power of under 28 nW. By applying the inverse of the measured spectral phase via a programmable pulse shaper, we compress the distorted pulses from more than 3 ps to nearly bandwidth-limited durations of less than 500 fs. Our results show that SHG FROG measurements performed by using fiber-pigtailed aperiodically poled lithium niobate waveguides can serve as a robust and sensitive tool for characterization of PMD-induced spectral phase.
![Research paper thumbnail of Ultralow-power second-harmonic generation frequency-resolved optical gating using aperiodically poled lithium niobate waveguides [Invited]](https://attachments.academia-assets.com/86995025/thumbnails/1.jpg)
Journal of the Optical Society of America B, 2008
We discuss ultralow-power second-harmonic generation (SHG) frequency-resolved optical gating (FRO... more We discuss ultralow-power second-harmonic generation (SHG) frequency-resolved optical gating (FROG) in the telecommunication C-band using aperiodically poled lithium niobate (A-PPLN) waveguides as the nonlinear medium. A key theme of this work is that the phase-matching curve of the nonlinear medium is engineered to obtain an optical bandwidth adequate for measurement of subpicosecond pulses while retaining the optimum nonlinear efficiency consistent with this constraint. Our experiments demonstrate measurement sensitivity (defined as the minimum product of the peak and average pulse powers at which a reliable nonlinear signal can be detected) of 2.0ϫ 10 −6 mW 2 in a collinear SHG FROG geometry, approximately 5 orders of magnitude better than previously reported for any FROG measurement modality. We also discuss asymmetric Y-junction A-PPLN waveguides that permit background-free SHG FROG and a polarization-insensitive SHG FROG technique that eliminates the impairment that frequency-independent random polarization fluctuations induce in the FROG measurement. Finally, we applied these SHG FROG techniques in chromatic dispersion and polarization mode dispersion compensation experiments. In these experiments the FROG data enabled complete correction of distortions incurred by subpicosecond pulses passing through optical fibers; these results also demonstrate the ability to retrieve extremely complex pulses with high accuracy.
Journal of Lightwave Technology, 2006
Polarization mode dispersion (PMD) is a potential limiting factor in long-haul high-speed optical... more Polarization mode dispersion (PMD) is a potential limiting factor in long-haul high-speed optical communications, especially in systems beyond 10 Gb/s. Although considerable effort has been devoted to compensation methods for PMD, most of the research is restricted to a small bandwidth, within the limits of the first-and second-order PMD approximations. For the first-order approximation to be valid, the distortions induced by PMD must remain less than a few tenths of the pulse duration or the bit period for return-to-zero (RZ) or non-return-to-zero (NRZ) systems, respectively. In this work, as far as the authors know, the application of ultrafast optical pulse-shaping techniques for experimental broadband all-order PMD compensation is demonstrated for the first time. PMD is treated as arbitrary variations of state of polarization (SOP) and phase versus wavelength, in an all-order sense. Two fiber-pigtailed pulse shapers are implemented in a serial manner to compensate the polarization and phase spectra independently. The first step corrects the wavelength-dependent polarization states to a fixed wavelength-independent state. This reduces the PMD compensation problem to a generalized chromatic dispersion compensation problem. Consequently, equalization of the spectral phase in the second step restores the clean broadband pulse signal. In the experiments, compensation of subpicosecond pulses (14 nm bandwidth around 1550 nm) that are anomalously spread to more than 2 ps due to PMD is demonstrated. These results are potentially relevant for future ultrahigh-speed time-division-multiplexed (TDM) systems. Research challenges that must be addressed to bring this approach to practical application are also briefly enumerated, and the potential for scaling to a range compatible with wavelength-divisionmultiplexed (WDM) systems is discussed.
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Papers by Rostislav Roussev