Improvement of catastrophic optical damage (COD) level forhigh-power 0.98-μm GaInAs-GaInP laser

We investigate improvement of catastrophic optical damage (COD) level for Al-free 0.98-μm ridge waveguide laser diodes (LDs) using the impurity induced layer disordering (IILD) process applied near the facets. The IILD is used for the purpose of forming transparent windows near both facets of the LDs utilizing its ability to increase bandgap energy of the GaInAs-GaInAsP strained quantum-well (QW) active layer. Improvement of the cod level by at least 1.65 times compared to the conventional LDs is obtained for the LDs with Si⁺ implantation followed by annealing at 900°C for 10 min     

Aging time dependence of catastrophic optical damage (COD) failureof a 0.98-μm GaInAs-GaInP strained quantum-well laser

In this paper, we studied the aging time dependence of the catastrophic optical damage (COD) failure of an Al-free uncoated 0.98-μm GaInAs-GaInP strained quantum-well laser with an injection current as a parameter. Based on the stress-strength model, we first investigated experimentally the dependence of the critical power level (CPL) at which COD would take place upon the aging time. Then applying a statistical treatment to this result, we found for the first time that CPL data at each aging time could be considered to distribute according to the Weibull statistics, and the decrease rate of the CPL with the aging time depended very strongly on the injection current. Finally, using the relationship between the decrease rate of the CPL with the aging time and the current, we predicted roughly the time of a COD failure occurrence for both large and small current cases. As a result, we clarified that for our Al-free uncoated 0.98-μm laser, a COD failure became a fatal problem in the case of a large-current (high-power) operation     

Compact and highly efficient fiber amplifier modules pumped by a0.98-μm laser diode

Highly efficient and small-size erbium-doped fibers with a gain coefficient of 4.9 dB/mW and a strained quantum-well-type InGaAs laser diode with a lasing wavelength of 0.98 μm as a pumped light source. As a result, the module 4×6×1.5 cm, realized a maximum net gain of 33 dB with an electricity consumption of only 175 mW, which corresponds to a drive current of 80 mA. The module consists of four individual components: a pumping laser diode submodule, a wavelength-division-multiplexing-type fiber coupler, a polarization-insensitive optical isolator, and an erbium-doped single-mode fiber coil     

1.17-μm highly strained GaInAs-GaAs quantum-well laser

Excellent lasing properties and temperature characteristic of a highly strained 1.17-μm GaInAs-GaAs double-quantum-well laser are reported. We show that a strained buffer layer, which is employed in the device, has no tradeoff on the device performance. For a 1500-μm-long laser with cleaved facets a threshold current density of 200 A/cm² is achieved. A transparency current density of 180 A/cm² is estimated for as cleaved devices. A record high characteristic temperature in this wavelength range of 150 K is achieved     

1.3-μm Pr-doped In-Ga-based fluoride fiber amplifiers pumped bygrating-fiber-pigtailed 0.98-μm-band laser diodes with a detunedwavelength of 1 μm

At most efficient pump wavelength, a praseodymium-doped In-Ga-based fluoride fiber is directly pumped by four 0.98-μm-band laser diodes. These lasing wavelengths are detuned from 0.98 to 1 μm by external selective optical feedback from fiber grating reflectors. Maximum signal output power of +13.5 dBm is obtained at 1.296 μm. Four-wavelength multiplexed signals at 1.296-1.311 μm are amplified with a deviation of gain less than 1.9 dB. By using the amplifier as a power booster, data of 2.5 Gb/s is successfully transmitted more than 100 km     

A 7-μm praseodymium-based solid-state laser

We report the first demonstration of laser emission from the ³F₃ to ³F₂ transition in the rare earth praseodymium. This new 7-μm solid-state laser operates with an optical efficiency of 2.3% at 293 K and 10% at 150 K using an upconversion pumping mechanism. A discussion of the dynamics in this new laser material is included     

High-power operation in 0.98-μm strained-layer InGaAs-GaAssingle-quantum-well ridge waveguide lasers

High power strained-layer InGaAs-GaAs graded-index separate confinement heterostructure (GRIN-SCH) single-quantum-well (SQW) lasers at an emission wavelength of 0.98 μm have been fabricated. A light power as high as 270 mW and a maximum front power conversion efficiency of 51.5% have been obtained for the antireflective and highly-reflective coated laser with 9-μm-wide ridge and 600-μm-long cavity     

A 1.6-μm pumped 1.9-μm thulium-doped fluoride fiber laser andamplifier of very high efficiency

Results are presented for color center, and semiconductor, laser pumping of the 1.82 μm transition in a thulium-doped fluoride fiber. As an amplifier small signal gain efficiencies of 8.1 dB/mN were attained with a maximum gain of 36.5 dB being achieved for around 17-18 mW of launched pump power. As a laser a maximum slope efficiency of 84% and a minimum threshold for oscillation of 330 μW was also demonstrated for this system. Furthermore by suppressing all reflections down to <36 dB superfluorescent or ASE output was observed. In achieving efficient operation with a diode laser pump source this system shows strong commercial potential     

Temperature dependence of light-current characteristics of0.98-μm Al-free strained-quantum-well lasers

The decrease of the differential efficiency of 0.98-μm semiconductor lasers with temperature can make high power, high temperature applications difficult. We present an experimental and theoretical study of the temperature dependence of the internal quantum efficiency, internal loss and differential gain of 0.98-μm InGaAs/InGaAsP/InGaP strained quantum well lasers. In contrast to some earlier results, our measurements show the dominance of internal loss, attributed to free carrier absorption, in determining the temperature dependence of the differential efficiency, and show that leakage current is negligible below 120°C     

Low-threshold oxide-confined 1.3-μm quantum-dot laser

Data are presented on low threshold, 1.3-μm oxide-confined InGaAs-GaAs quantum dot lasers. A very low continuous-wave threshold current of 1.2 mA with a threshold current density of 28 A/cm² is achieved with p-up mounting at room temperature. For slightly larger devices the continuous-wave threshold current density is as low as 19 A/cm²     

A 1.55-μm solid-state laser source for DWDM applications

We describe the design and operation of a 1550-nm diode pumped Er,Yb:glass laser with >130 mW of output power and a free running linewidth of ~22 kHz. Due to the low frequency relaxation oscillation, near shot limited relative intensity noise performance is obtained throughout the radio frequency (RF) range of interest for cable television and dense wavelength division multiplexed (CATV/DWDM) applications. For long-haul spans an intracavity lithium niobate phase modulator allows for chirping of the linewidth to bandwidths and at rates sufficient to defeat stimulated Brillouin scattering (SBS). For certain applications, the high output power can eliminate the need for an erbium-doped fiber amplifier (EDFA)     

1.5-μm wavelength tunable phase-shift-controlled distributedfeedback laser

A 1.5 μm wavelength tunable phase-shift-controlled distributed feedback laser diode is studied. This wavelength tunable laser controls the light output power and the oscillation wavelength independently by current injection. During wavelength tuning, the submode suppression ratio is large and an almost constant spectral linewidth from 24 to 29 MHz is achieved over a wavelength tuning range as wide as 113 GHz (9.0 Å). The threshold gain change and the loss change are small during wavelength tuning and as a result an almost constant light output power is achieved     

1.15-μm wavelength oxide-confined quantum-dot vertical-cavitysurface-emitting laser

Low-threshold lasing is achieved at 1.154 μm for an oxide-confined quantum-dot (QD) vertical-cavity surface-emitting laser (VCSEL) grown on a GaAs substrate. The long wavelength emission is obtained through use of an InAs-GaAs QD active region. A continuous-wave (CW) threshold of 502 μA is obtained for a device size of 10-μm diameter, corresponding to a threshold current density of 640 A/cm²      

3.6-MHz linewidth 1.55-μm monomode vertical-cavitysurface-emitting laser

We report on high-resolution linewidth measurement of proton-implanted bottom-emitting InGaAsP long-wavelength vertical-cavity surface-emitting lasers (VCSELs) employing the heterodyne method. Devices with 35-μm active diameter exhibit record linewidths of 3.6 MHz and negligible extrapolated linewidth for infinite power, at room temperature. This result relies on the long-cavity-designed VCSEL. The linewidth enhancement factor is also determined: α≈2.1     

All-selective MOVPE-grown 1.3-μm strained multi-quantum-wellburied-heterostructure laser diodes

Strained InGaAsP multi-quantum-well (MQW) double-channel planar-buried-hetero (DC-PBH) laser diodes (LDs) were fabricated by selective metalorganic-vapor-phase epitaxy (MOVPE). In the laser fabrication process, both the strained MQW active layer and current blocking structure were directly formed by selective MOVPE without any semiconductor etching process. The LDs are called all-selective MOVPE-grown BH LDs. The laser fabrication process can achieve both a precisely controlled gain waveguide structure and an excellent current blocking configuration, realizing the optimized DC-PBH structure. These aspects are essential to the high-performance and low-cost LD, which is strongly demanded for optical access network systems or fiber-to-the-home networks. This paper will show the excellent high-temperature characteristics for 1.3-μm Fabry-Perot LDs which have a record threshold current of 18 mA with a low-operation current of 56 mA for 10 mW, and 74 mA for 15 mW at 100°C with extremely high uniformity. Furthermore, reliable long-term operation at high temperature (85°C) and high-output power of 15 mW has been demonstrated for the first time     

High-coupling-efficient 1.3-μm laser diodes with goodtemperature characteristics

We have proposed uniformly beam-expanded structures based on the advanced concept for realizing high coupling efficiency and good temperature characteristics. Beam expansion (optical confinement reduction) by narrowing the core layer width as well as a carrier confinement are strongly enhanced by adopting a larger bandgap InGaAsP for MQW barriers and separate confinement heterostructure layers. These laser diodes (LD's) were fabricated by the conventional buried heterostructure laser process, which is very important in reducing the cost. Our results have proven the effectiveness of our proposition. The LD's with high coupling efficiency (-3.2 dB) and good temperature characteristics have been achieved even using the simple approach of reducing optical confinement. The threshold currents at 25 and 85°C are 9.3 and 39.4 mA, respectively. The slope efficiency at 25°C is 0.39 W/A and still high (0.26 W/A) even at 85°C     

Slab-coupled 1.3-μm semiconductor laser with single-spatiallarge-diameter mode

A high brightness semiconductor diode laser structure, which utilizes a slab-coupled optical waveguide region to achieve several potentially important advances in performance, is proposed and experimentally demonstrated using a simple rib waveguide in an InGaAsP-InP quantum-well structure operating at 1.3-μm wavelength. These lasers operate in a large low-aspect-ratio lowest-order spatial mode, which can be butt coupled to a single-mode fiber with high coupling efficiency     

11.5-W CW 1.83-μm diode laser array

We demonstrate high-power operation of both individual broad-waveguide separate-confinement-heterostructure quantum-well InGaAsP-InP laser diodes and 1-cm-wide arrays emitting at 1.83 μm. Despite strong dependence of threshold current density and diode efficiency on operating temperature, a continuous-wave output power of 2.1 W has been obtained for 100-μm-aperture lasers with 2-mm-long cavities. An output power of 11.5 W was reached for ten element 1-cm-wide array at a heatsink temperature of 16°C     

High-power 0.98-μm strained quantum-well lasers fabricated usingin situ monitored reactive ion beam etching

0.98-μm wavelength InGaAs-AlGaAs strained quantum-well buried ridge lasers were fabricated using in situ monitored reactive ion beam etching (RIBE). This technique allowed a very accurate ridge geometry, resulting in high single transverse-mode power more than 250 mW and high-fiber coupled power more than 150 mW     

A 1.54-μm monolithic semiconductor ring laser: CW andmode-locked operation

The authors have fabricated a monolithic semiconductor ring laser with a diameter of 3.0 mm. A straight tangent waveguide provides two output ports through evanescent coupling. The laser, which exhibits a threshold current of 157 mA, operates in a single longitudinal mode with a linewidth of 900 kHz at a wavelength of 1.54 μm. The device has been actively mode-locked at the fundamental resonance frequency of 9.0 GHz, yielding 27-ps pulses with a time-bandwidth product of 0.47. Differences in the characteristics of the pulses emitted from the two output ports indicate counterpropagating pulse trains, which because of the mode-locking scheme must collide in the modulated gain section