InGaAs-GaAs-InGaP distributed feedback buried heterostructurestrained quantum-well lasers for high-power operation at 0.98 μm

Data are presented on device results from InGaAs-GaAs distributed feedback buried heterostructure (DFB BH) strained-quantum-well lasers with InGaP cladding layers. DFB BH lasers with a p-n InGaP current blocking junction entirely grown by a three-step MOVPE on GaAs substrates show a low laser threshold of 3.2 mA and a high output power of 41 mW with single-longitudinal-mode operation, both measured CW at RT. The monomode oscillation is obtained even at the injection current of 140 mA (44 times the laser threshold) with the side-mode suppression ratio of 35 dB and the temperature sensitivity of Bragg modes being 0.5 Å/°C measured between 20 and 40°C     

Very low threshold operation of 1.52 μm GaInAsP/InP DFB buriedridge structure laser diodes entirely grown by MOCVD

1.52 μm GaInAsP/InP DFB laser diodes with a buried ridge structure were fabricated entirely by MOCVD, with a second-order corrugation on the GaInAsP guiding layer. The 5 mA minimum threshold current achieved is believed to be the lowest yet reported for DFB lasers. Single longitudinal-mode operation with a side-mode suppression ratio greater than 35 dB was obtained from 20°C (up to 16 mW) to 90°C (up to 3 mW)     

Long-wavelength InGaAsP/InP distributed feedback lasersincorporating gain-coupled mechanism

Successful operation of long-wavelength InGaAsP low-threshold-current gain-coupled DFB lasers was demonstrated by using an InGaAsP quaternary grating that absorbs the DFB (distributed feedback) emission. The amount of gain (loss)-coupling is controlled by the composition (bandgap) and thickness of the grating quaternary and the InP-spacer layer between the grating and the active layer. With optimally designed lasers, CW (continuous-wave) threshold currents were 10-15 mA (250-μm cavity, as-cleaved), slope efficiency was ~0.4 mW/mA (both facets) and SMSR (side-mode suppression ratio) was as high as 52 dB. The laser operated in the same DFB mode with SMSR staying ~50 dB throughout the entire current range. At 100°C, the CW threshold current stayed low, ~50 mA, and SMSR was ~40 dB. Results also indicate that the presence of gain-coupling removes the degeneracy in lasing wavelength     

2.05-μm wavelength InGaAs-InGaAs distributed-feedbackmultiquantum-well lasers with 10-mW output power

Single-mode operation beyond 2.05-μm wavelength has been achieved in InGaAs-InGaAs distributed-feedback (DFB) laser with four quantum wells. The continuous-wave output power is 10.5 mW at a drive current of 200 mA and 25°C, The tuning range of the wavelength is between 2.051-2.056 μm with a temperature tuning rate of +0.125 nm/°C     

High slope efficiency and low noise characteristics intapered-active-stripe DFB lasers with narrow beam divergence

We report high slope efficiency and low noise characteristics in a distributed feedback (DFB) laser lasing at 1.3 μm with narrow beam divergence by employment of a laterally tapered active stripe over the whole cavity. This tapered structure is designed to realize narrow beam divergence, low threshold current, and high longitudinal mode selectivity. The fabricated tapered-active-stripe DFB lasers demonstrated of 9.20×13.40 and a record slope efficiency, for a narrow beam DFB laser, of 0.59 mW/mA. The temperature characteristics from -10°C to 85°C shows high output power at high temperature, stable single longitudinal mode oscillation and stable far-field patterns. Furthermore, for the first time ever, a low relative intensity noise characteristic of under -155 dB/Hz has been realized when butt-coupling into a single-mode fiber     

2-μm GaInSb-AlGaAsSb distributed-feedback lasers

Room temperature continuous-wave operation of 2-μm single-mode InGaSb-AlGaAsSb distributed-feedback (DFB) lasers has been realized. The laser structure has been grown by solid source molecular beam epitaxy (MBE). Single-mode DFB emission is obtained by first-order Cr-Bragg gratings on both sides of the laser ridge. For a cavity with 900 μm length and 4 μm width, the threshold currents are around 20 mA and the continuous-wave output power is 10 mW at a drive current of 200 mA at 20°C. Monomode emission with sidemode suppression ratios of 31 dB has been obtained     

Wideband HEMT MMIC low-noise amplifier with temperaturecompensation

A wideband low-noise pseudomorphic HEMT MMIC variable-gain amplifier has been designed and fabricated. The amplifier has a nominal gain of 13 dB across the band 2-20 GHz, with gain flatness better than ±0.4 dB. The noise figure is less than 3 dB across the band 6-16 GHz. An on-chip temperature-sensing diode is used to provide a linear temperature correction which has been used to reduce the gain variation of the amplifier by a factor of 2 across the temperature range -50°C to +95°C     

Wide Temperature Range Operation of a 1.55-$mu$m 40-Gb/s Electroabsorption Modulator Integrated DFB Laser for Very Short-Reach Applications

We present the uncooled operation of a 1.55- mum 40-Gb/s InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser within a temperature range of 95degC (-15degC to 80degC ). To the best of our knowledge, this is the largest temperature range reported so far for such a 40-Gb/s EAM integrated DFB laser. We designed the EAM to operate at high speed by reducing the electrical parasitics, and we achieved a 3-dB frequency bandwidth of over 39 GHz for an EAM length of less than 150 mum. We demonstrated a 2-km single-mode fiber (SMF) transmission at 40-Gb/s over a wide temperature range of -15degC to 80degC by adjusting only the bias voltage to the EAM while keeping the modulation voltage swing constant at 2.0 V when the temperature changed. We achieved a dynamic extinction ratio of over 8.2 dB and a 2-km SMF transmission with a power penalty of less than 2 dB over a wide temperature range.     

Laterally coupled strained MQW ridge waveguide distributed-feedbacklaser diode fabricated by wet-dry hybrid etching process

The fabrication and the characteristics of the laterally coupled GaInAsP-InP quantum-well ridge waveguide distributed-feedback (DFB) lasers are presented. The electron beam (EB) lithography and the wet and dry hybrid etching technique have been used to fabricate the deep grating structures for the DFB lasers on and beside the sidewalls of the narrow ridge waveguide. The threshold current was 18.5 mA at 20°C, and the sidemode suppression ratios (SMSRs) were ensured to be more than 40 dB for as-cleaved devices with various cavity lengths. The continuous-wave output powers of over 15 mW/facet have been observed, while transverse and longitudinal modes have remained in single mode at this output level     

Performance limitations of high-power DFB fiber lasers

In this letter, we experimentally study several different configurations of high-power single-frequency sources based on distributed-feedback fiber laser (DFB FL). In particular, we have compared two schemes in terms of pumping efficiency, relative intensity noise (RIN) and optical signal-to-noise ratio (OSNR): directly pumped DFB FLs pumped by a high-power fiber-based pump source (stand-alone DFB FL) and a combination of a DFB FL and a power amplifier (amplified DFB FL). At the output powers below 40 mW, a stand-alone DFB FL has the highest OSNR (> 63 dB) and the lowest RIN (< -165 dB/Hz). The net efficiency of a stand-alone DFB FL can be doubled by using an amplified DFB FL at the expense of degraded OSNR and RIN. It is also shown that RIN below -160 dB/Hz and OSNR > 60 dB can be achieved by an amplified DFB with output power greater than 1 W.     

Optimum design of waveguide E-plane stub-loaded phaseshifters

Broadband low-insertion-loss E-plane stub-loaded rectangular waveguide phase shifters are designed with the method of field expansion into normalized eigenmodes, which includes higher-order mode interaction between the step discontinuities. Computer-optimized three-stub prototypes of 90° differential phase shift with reference to an empty waveguide of appropriate length, designed for R140-band (12.4-18 GHz) and R320-band (26.5-40 GHz) waveguides, achieve typically ±0.5° phase shift deviation within about 20% bandwidth. For two-stub designs, the corresponding values are about +2.5°/-1° and 17%. Both designs achieve minimum return loss of 30 dB. The theory is verified by measurements of a compact R120-band (10-15 GHz) waveguide phase shifter design example milled from a solid block, showing measured insertion loss of about 0.1 dB and about +2.5°/-0.5° phase error between 10.7 and 12.7 GHz     

Continuous-wave operation of single-transverse-mode 1310-nm VCSELsup to 115°C

Long-wavelength vertical cavity surface emitting lasers (VCSELs) have thus far not provided substantial continuous-wave (CW) output power above 70°C. We describe recent advances using a vertically integrated 850 nm optical pump with a 1310-nm VCSEL. Using this approach, the devices described demonstrate record high temperature performance. We show single-transverse mode CW operation from -40 to +115°C, 0.5 mw optical power up to +85°C, and excellent device uniformity     

1.3-μm GaInAsP/InP transverse-mode stabilized buried-crescentlasers by a new fabrication technique using a reactive ion beam etching

Transverse-mode-stabilized, 1.3-μm, GaInAsP/InP, buried-crescent (BC) lasers fabricated using a reactive ion beam etching (RIBE) technique are presented. Yields of single-transverse-mode operation as high as 95% are achieved with low threshold currents of 11-25 mA. Transverse-mode stability under both high-power and long-term operation (50°C, 20 mW, 1000 h) is demonstrated. A coupling efficiency into a single-mode fiber of 63% and a coupled power of 40 mW at 160 mA are achieved. Stable continuous-wave operation is also confirmed under a constant power of 5 mW (50 and 70°C) and 20 mW (50°C) in an aging test     

1.55-/spl mu/m DFB lasers utilizing an automatically buried absorptive InAsP layer having a high single-mode yield

We describe 1.55-/spl mu/m distributed feedback laser diodes (DFB LDs) having a single-mode (SM) yield as high as 80% and 93% for as-cleaved and antireflection/high reflection (AR/HR=3%/95%) coated devices, respectively. The high SM yield was achieved by introducing an automatically buried InAsP layer between a concave of InP corrugations and an overgrown layer. The use of the automatically buried InAsP layer implemented by a single step growth makes the device fabrication process much easier than that of conventional loss-coupled DFB LDs. Fabricated DFB LDs with AR/HR-coated facets showed a low threshold current of 8 mA (34 mA) and a high slope efficiency of 0.32 mW/mA (0.22 mW/mA) at 25/spl deg/C (85/spl deg/C). A sidemode suppression ratio better than 40 dB was obtained for the temperature range between -20/spl deg/C and 85/spl deg/C and the injection current range between 20 and 100 mA.     

Resin selection and high-speed coating of optical fibers withUV-curable materials

As a result of the curing properties of UV-curable resins, a selection criterion for UV-curable resins for high-speed fiber coating is proposed. The method is based on specifying two parameters of a UV-curable resin, which designate the Yong's modulus of cured resin. The method was used to coat graded-index fibers with the selected resins and it was demonstrated that the optical loss changes due to the coating process are small. The change of the fiber ribbon was within 0.1 dB/km under temperature changes between -40 °C and +60 °C     

1.3-μm GaInNAs-AlGaAs distributed feedback lasers

Room temperature continuous-wave operation of 1.3-μm single-mode GaInNAs-AlGaAs distributed feedback (DFB)-lasers has been realized. The laser structure has been grown by solid source molecular beam epitaxy (MBE) using an electron cyclotron resonance plasma source for nitrogen activation (ECR-MBE). Laterally to the laser ridge a metal grating is patterned in order to obtain DFB. The evanescent field of the laser mode couples to the grating resulting in single-mode DFB emission. The continuous wave threshold currents are around 120 mA for a cavity with 800-μm length and 2 μm width. Monomode emission with side-mode suppression ratios of nearly 40 dB have been obtained     

A CMOS bandgap reference for differential signal processing

A switched-capacitor fully differential bandgap reference that uses a standard double-poly CMOS process is presented. It generates a differential reference voltage of 6.2 V with a standard deviation of about 24 mV and a typical temperature stability of 15.2 p.p.m./°C over an extended temperature range from -40 to +85°C. These performance results are obtained without using any trimming in mass production. The bandgap reference only occupies 730 mil² and dissipates 4.8 mW at±5-V power supplies. A measured power supply rejection of about 90 dB until 500 kHz is the best ever reported at high frequency     

Development of the ERS-1 active radar calibration unit

The development of a microwave active radar calibration unit (ARC) to be used as a ground calibration reference standard for the European Remote Sensing Satellite ERS-1 imaging synthetic aperture radar is described. Three such units are placed across the radar swath, giving point target returns with a known signal strength, and are used to calibrate the radar image. The units have been designed for maximum stability with temperature (<0.1 dB over the temperature range of -15°C to +35°C). For absolute calibration the ARC is referenced to a flat plate using a novel technique of multiple transmission in its self-calibration mode, achieving an absolute calibration error of <0.14 dB     

1.3 mu m semiconductor laser power amplifier

The performance of a 3.4-Gb/s system using a low-power 1.318- mu m distributed-feedback (DFB) laser transmitter and a traveling-wave semiconductor laser power amplifier is studied. The -14.5-dBm, input from a directly modulated DFB laser is boosted to +10.3 dBm, of which +4.8 dBm is coupled into the transmission fiber. The penalty, caused by amplifier noise and pattern effects due to gain saturation, is less than 0.5 dB.<>     

20 Gbit/s, 1.55 μm strained-InGaAsP MQW modulator integrated DFBlaser module

The high-speed (20 Gbit/s) and highly efficient (2 V peak to peak for a 22 dB on/off ratio) operation of an MQW integrated electroabsorption modulator/DFB laser module is demonstrated. Output power from the module is over +3 dBm in the pigtailed singlemode fibre. To the authors' knowledge, this is the first report of 20 Gbit/s operation with a monolithically integrated light source