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Dive into the research topics where Yuliya A. Akulova is active.

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Featured researches published by Yuliya A. Akulova.


IEEE Journal of Selected Topics in Quantum Electronics | 2002

Widely tunable electroabsorption-modulated sampled-grating DBR laser transmitter

Yuliya A. Akulova; Gregory Fish; Ping-Chiek Koh; Clint L. Schow; P. Kozodoy; Anders Dahl; Shigeru Nakagawa; M.C. Larson; Michael Mack; Timothy A. Strand; Christopher W. Coldren; E.R. Hegblom; Steven Penniman; T. Wipiejewski; Larry A. Coldren

We report on a widely tunable transmitter based on a sampled-grating distributed Bragg reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption (EA) modulator. Modulated time-averaged powers in excess of 5 dBm, RF extinction ratios >10 dB, and error-free transmission at 2.5 Gb/s for 350 km of standard single-mode fiber have been demonstrated across a 40-nm tuning range. In CW mode of operation, the module meets all long-haul system requirements for externally modulated laser sources: stability, power (>10 mW), RIN ( 100 yr for output wavelength stability and power across all channels.


IEEE Photonics Technology Letters | 2005

40-GHz dual-mode-locked widely tunable sampled-grating DBR laser

Leif A. Johansson; Zhaoyang Hu; Daniel J. Blumenthal; Larry A. Coldren; Yuliya A. Akulova; Greg A. Fish

Generation of 40-GHz alternate-phase pulses is demonstrated using a dual-mode-locked sampled-grating distributed Bragg reflector laser. More than 10-dB extinction and >20-dB sidemode suppression ratio is measured over the >40-nm tuning range of the laser. Based on captured phase noise spectra, the timing jitter is estimated in the 0.35-0.41-ps range. The demonstrated dual-mode laser would form an attractive basis for an integrated 40-Gb/s return-to-zero transmitter.


Journal of Lightwave Technology | 2003

Sampled-grating DBR laser-based analog optical transmitters

Leif A. Johansson; J.T. Getty; Yuliya A. Akulova; Gregory Fish; Larry A. Coldren

Sampled-grating distributed Bragg grating (SGDBR) laser-based widely tunable optical transmitters are investigated for application in high-performance analog links. More than 45 nm tuning range, 40 dB sidemode suppression ratio, and peak relative intensity noise below -153 dB/Hz is measured. SGDBR lasers integrated with semiconductor optical amplifiers and electroabsorption modulators (EAMs) are characterized with spurious free dynamic range of 125-127 dB/spl middot/Hz/sup 4/5/ over the wavelength tuning range. It is also shown how the modulation response of the EAM is affected by the optical power to limit the performance of the analog transmitter.


IEEE Photonics Technology Letters | 2002

Direct intensity modulation in sampled-grating DBR lasers

M.L. Majewski; Jonathon S. Barton; Larry A. Coldren; Yuliya A. Akulova; M.C. Larson

In this letter, we present new experimental results obtained for direct intensity modulation of widely tunable sampled-grating distributed Bragg-reflector (SGDBR) lasers. These results are of significance to SGDBR applications in wavelength-division-multiplexing systems. The devices described operate in the C-band (wavelength range 1525-1565 nm). A 6-GHz small-signal modulation bandwidth and >10-dB signal extinction ratio under large-signal operation were obtained. We have also recorded an undistorted eye pattern for a nonreturn-to-zero random signal 2/sup 31/-1 word length at 2.5-Gb/s bit rate during transmission over 75-km of standard single-mode fiber.


IEEE Transactions on Components and Packaging Technologies | 2005

Thermal effects in monolithically integrated tunable laser transmitters

P. Kozodoy; Timothy A. Strand; Yuliya A. Akulova; Gregory Fish; Clint L. Schow; Ping-Chiek Koh; Zhixi Bian; James Christofferson; Ali Shakouri

We investigate thermal effects in widely-tunable laser transmitters based on an integrated single chip design. The chip contains a Sampled-Grating Distributed Bragg Reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption modulator (EAM). The thermal impedance of the ridge structure is evaluated through simulation and experiment, and thermal crosstalk between sections is examined. Heating of the mirrors by neighboring sections is found to result in unintentional offsets in wavelength tuning. Thermal effects in the electroabsorption modulator are examined in depth. A positive feedback mechanism causes local temperature rise at the modulator input, with the potential to trigger catastrophic thermal runaway. A self-consistent finite-element model is developed to simulate the EAM temperature profile and device performance. This model is used to optimize the device, resulting in integrated EAMs that achieve a dissipated power limit in excess of 300 mW.


Novel In-Plane Semiconductor Lasers II | 2003

High performance widely-tunable SG-DBR lasers

M.C. Larson; Yuliya A. Akulova; Christopher W. Coldren; Thomas Liljeberg; Gregory A. Fish; S. Nakagawa; Anders Dahl; P. Kozodoy; Doreen Bingo; Ming Bai; Nitya Ramdas; Steven Penniman; T. Wipiejewski; Larry A. Coldren

Widely-tunable sampled-grating distributed Bragg reflector (SG-DBR) lasers with integrated Semiconductor Optical Amplifiers (SOAs) simultaneously exhibit high (20 mW CW) fiber-coupled output power, high side mode suppression ratio, low noise (below -140 dB/Hz RIN), low line-width (<5 MHz), and high reliability, across a 40 nm C-band tuning range.


optical fiber communication conference | 2002

Widely-tunable electroabsorption-modulated sampled grating DBR laser integrated with semiconductor optical amplifier

Yuliya A. Akulova; Clint L. Schow; A. Karim; Shigeru Nakagawa; P. Kozodoy; Gregory Fish; J. DeFranco; Anders Dahl; Mike Larson; T. Wipiejewski; D. Pavinski; T. Butrie; Larry A. Coldren

Summary form only given. We have demonstrated a widely-tunable, 2.5 Gb/s transmitter based on a SG-DBR laser monolithically integrated with a SOA and electroabsorption modulator. Time-averaged powers in excess of 3 dBm and RF extinction ratio >10 dB across a 40 nm tuning range have been achieved. Error-free transmission at 2.5 Gb/s has been demonstrated for 200 km of standard single mode fiber.


Photonics packaging and integration. Conference | 2003

Integration of active optical components

T. Wipiejewski; Yuliya A. Akulova; Gregory Fish; Clint L. Schow; Ping Koh; Adil Karim; Shigeru Nakagawa; Anders Dahl; P. Kozodoy; Alex Matson; Bradley W. Short; Chuck Turner; Steven Penniman; M.C. Larson; Christopher W. Coldren; Larry A. Coldren

Integration of active optical components typically serves five goals: enhanced performance, smaller space, lower power dissipation, higher reliability, and lower cost. We are manufacturing widely tunable laser diodes with an integrated high speed electro absorption modulator for metro and all-optical switching applications. The monolithic integration combines the functions of high power laser light generation, wavelength tuning over the entire C-band, and high speed signal modulation in a single chip. The laser section of the chip contains two sampled grating DBRs with a gain and a phase section between them. The emission wavelength is tuned by current injection into the waveguide layers of the DBR and phase sections. The laser light passes through an integrated optical amplifier before reaching the modulator section on the chip. The amplifier boosts the cw output power of the laser and provides a convenient way of power leveling. The modulator is based on the Franz-Keldysh effect for a wide band of operation. The common waveguide through all sections minimizes optical coupling losses. The packaging of the monolithically integrated chip is much simpler compared to a discrete or hybrid solution using a laser chip, an SOA, and an external modulator. Since only one optical fiber coupling is required, the overall packaging cost of the transmitter module is largely reduced. Error free transmission at 2.5Gbit/s over 200km of standard single mode fiber is obtained with less than 1dB of dispersion penalty.


IEEE Photonics Technology Letters | 1997

Low-threshold 840-nm laterally oxidized vertical-cavity lasers using AlInGaAs-AlGaAs strained active layers

J. Ko; E.R. Hegblom; Yuliya A. Akulova; Brian Thibeault; Larry A. Coldren

We explore the use of a novel strained AlInGaAs-AlGaAs material system to achieve low-threshold current in oxide-apertured vertical-cavity lasers (VCLs) emitting near 850 nm. We report a low continuous-wave (CW) room-temperature threshold current of 290 /spl mu/A from top-emitting, 840-nm VCLs with a 5-/spl mu/m-wide thin-oxide aperture. The low-threshold current has been attributed to the use of strained active layers, which increase the gain and reduce the transparency current. We also studied the effects of post-growth rapid thermal annealing (RTA) on the characteristics of AlInGaAs-AlGaAs VCLs and found that RTA improves the material quality and significantly enhances VCL performance.


Symposium on Electro-Optics: Present and Future (1998), paper CB3 | 1998

Vertical-Cavity Lasers for Parallel Optical Interconnects

Larry A. Coldren; E.R. Hegblom; Yuliya A. Akulova; J. Ko; Eva M. Strzelecka; Syn-Yem Hu

Continuing increases in efficiency, uniformity, and yield for low-threshold dielectrically Apertured Vertical-Cavity Surface-Emitting Lasers (VCSELs) suggest that this new generation of sources may be ready for insertion into practical parallel interconnect systems. This paper will review the recent evolution of these devices, pointing out key enabling advances and potential roadblocks yet to be addressed. Included will be advances that have led to record low optical losses as well as record high wall-plug efficiency at powers of a few hundred microwatts, desirable for massively parallel optical interconnects. The use of engineered oxide apertures is a key element in these cases. Experimental results will also include recent free-space and WDM fiber interconnects. Remaining issues to be addressed include some sort of lateral carrier confinement, such as a buried-heterostructure, to reduce carrier losses as devices are scaled to small lateral dimensions.

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P. Kozodoy

University of California

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T. Wipiejewski

University of California

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