Low threshold current density 1.3-μm strained-layer quantum-welllasers using n-type modulation doping

We have developed 1.3 μm n-type modulation-doped strained-layer quantum-well lasers. Modulation-doped lasers with long cavities (low threshold gain) exhibit much lower threshold current densities than conventional lasers with undoped barrier layers. The lowest threshold current density we obtained was 250 A/cm² for 1500 μm long lasers with five quantum wells. The estimated threshold current density for an infinite cavity length was 38 A/m²/well. This is the lowest value for InGaAsP-InGaAsP and InGaAs-InGaAsP quantum well lasers to our knowledge     

Optical and RF characteristics of short-cavity-lengthmultiquantum-well strained-layer lasers

The optical and RF characteristics of short-cavity, strained-layer In_0.3Ga_0.7As graded-index separate-confinement-heterostructure (GRINSCH) multiple-quantum-well ridge waveguide lasers are described. Short-cavity-length strained-layer lasers with four In_0.3Ga_0.7As quantum wells have been fabricated using chemically assisted ion beam etching (CAIBE). These lasers have a very low K factor of 0.14 ns and a high differential gain of 1.1×10^-15 cm². A 3 dB modulation bandwidth of 23.5 GHz has been measured on a 50 μm cavity-length device. This is the highest reported bandwidth for a quantum well laser     

Er3+-Yb3+ and Er3+ doped fiberlasers

Single-mode fiber lasers operating at ~1.57 μm are described. Output powers of >2 mW are reported for laser diode pumped operation. Direct comparison is made between fiber lasers using sensitized erbium (Er³⁺ and Yb³⁺) and erbium on its own. The performance of Er³⁺-Yb³⁺ fiber lasers is analyzed in more detail as a function of fiber length. Both CW and Q-switched operations are studied and the results obtained demonstrate that practical sources at 1.5 μm are available from diode pumped Er³⁺ -Yb³⁺ systems     

Improved performance of 2-μm GaInAs strained quantum-well laserson InP by increasing carrier confinement

We have fabricated and analyzed strained GaInAs quantum-well diode lasers emitting at wavelengths above 2 μm, grown by metal-organic chemical vapor phase epitaxy on InP substrates. To study the effect of carrier confinement on laser performance, lasers grown with nearly lattice matched ternary GaInAs barriers and quaternary GaInAsP barriers were compared. The use of quaternary barriers improves the device performance in terms of output power, emission wavelength, characteristic temperature, differential quantum efficiency, and power efficiency. Internal losses and internal quantum efficiency remain unchanged. At a heat sink temperature of 330 K index guided diode lasers with GaInAsP-barriers emitting at 2.092 μm showed a continuous-wave (CW) output power of 42 mW/facet     

Strained-layer InGaAs-GaAs-AlGaAs buried-heterostructure laserswith nonabsorbing mirrors by selective-area MOCVD

Design, fabrication, and operation of strained-layer InGaAs-GaAs-AlGaAs buried-heterostructure (BH) lasers with nonabsorbing mirrors fabricated by selective-area epitaxy (SAE) are presented. The SAE-BH lasers with nonabsorbing mirrors operate at powers up to ~325 mW/facet (4 μm wide output aperture), which is a >40% increase over conventional SAE-BH lasers     

Enhanced relaxation oscillation frequency of 1.3 μmstrained-layer multiquantum well lasers

Dependence of relaxation oscillation frequency (f_r) on the bandgap wavelength of InGaAsP barrier layers (λ_g ^b) and number of quantum wells (N_w) were investigated for the first time, for 1.3 μm InGaAsP/InGaAsP compressively strained multiquantum well (MQW) lasers. 1.3 times higher f_r was confirmed for strained-layer MQW lasers with large N _w (N_w⩾7) and wide bandgap barrier layers (λ_g^b=1.05 μm) at the same injection level, compared with unstrained MQW lasers having the same well thicknesses and the same emitting wavelength. This enhancement mainly results from increased differential gain due to strain effects separated from the quantum-size effect     

High-temperature performance of InGaAs-InGaAlAs-InP 1.79-μmdiode lasers grown in solid-source molecular-beam epitaxy

1.79-μm InGaAs-InGaAlAs strained-layer quantum-well diode lasers have been fabricated. A characteristic temperature of 72 K has been achieved. At a temperature as high as 100°C, a continuous-wave output power of more than 6.5 mW per facet has been demonstrated with lasers using as-cleaved facets as mirrors     

Continuous operation of high-power (200 mW) strained-layerGa1-xInxAs/GaAs quantum-well lasers with emissionwavelengths 0.87⩽λ⩽0.95 μm

Separate confinement single-quantum-well lasers with 100-120 Å-thick strained Ga_1-xIn_xAs/GaAs active layers have been grown on (100) GaAs substrates by metalorganic chemical vapour deposition. Ten-stripe proton-implanted arrays with 90 μm-wide aperture and 250 μm cavity length emit 200 mW CW optical power at wavelengths 0.87⩽λ⩽0.95 μm. Lifetest data on an uncoated device emitting 90 mW/facet at 50°C and λ=0.95 μm suggest a mean-time-to-failure in excess of 2500 h at room temperature. The performance of lasers with strained Ga_1-xIn_xAs quantum wells is comparable to that of unstrained Al_xGa_1-xAs/GaAs quantum-well lasers without facet coating     

High-power 2.0 μm InGaAsP laser diodes

Data detailing the performance of strained-layer InGaAs/InGaAsP double-quantum-well laser diodes operating at 2.0 μm are presented. The total external efficiency and maximum power achieved are 55% and 1.6-W continuous wave (CW), respectively, from a 200-μm gain-guided laser diode. Measurements on gain-guided broad area devices yield an internal efficiency of 0.73 with a distributed loss coefficient, α, of 7.5 cm^-1. The measured threshold current density is 300 A/cm² for a 2-mm-long broad area device operated CW at 25°C     

InxGa1-xAs-AlyGa1-yAs-GaAs strained-layer quantum-well heterostructure circular ringlasers

The growth, processing, and optical characterization of a single Y-junction In_xGa_1-xAs-Al_yGa_1-y As-GaAs strained-layer quantum-well heterostructure circular ring laser (6 μm width, 11~251 μm outer radius) are described. The circular ring lasers have been grown by metalorganic chemical vapor deposition, etched by SiCl₄ reactive ion etching, and planarized by polyimide. The dependences of laser threshold current density and peak emission wavelength (950~1015 nm) on outer radius are presented. The emission spectra show that the circular ring lasers lase mainly in high-order whispering gallery modes, with smaller outer radius ring lasers operating in low-order whispering gallery modes     

Dependence of differential quantum efficiency on the confinementstructure in InGaAs/InGaAsP strained-layer multiple quantum-well lasers

An internal efficiency of 91% was obtained with In_0.7Ga _0.3As/InGaAsP strained-layer multiple quantum well (MQW) lasers emitting at a wavelength of 1.5 μm. The dependence of the reciprocal differential quantum efficiency on the length of the laser cavity shows that the absorption loss in the InGaAsP (λ=1.3 μm) confinement layer caused by carrier overflowing into the confinement layer reduces the internal efficiency     

Tunable laser-diode-pumped Nd:YAG microcrystal lasers at 1.4 μm

TEM₀₀ laser operation of a monolithic Nd:YAG crystal laser has been achieved on three transitions at 1.414 μm, 1.444 μm and at 1.431 μm with laser diode pumping at 808 nm. The laser threshold was 1.5 W and the maximum output power 50 mW. The gain linewidths at 1.414 μm and 1.444 μm were determined by means of temperature tuning the microcrystal lasers. Calculations for designing tunable single frequency microcrystal lasers have been performed     

High-power single-mode 2.0 μm laser diodes

Data are presented on high-power single-mode index-guided laser diodes fabricated from a strained-layer InGaAs-InGaAsP double quantum well heterostructure epitaxial design. The total maximum power and external efficiency achieved are 50 mW and 43%, respectively. The far-field is measured to be 31° by 46° in the parallel and perpendicular directions, yielding an aspect ratio of 1.5 for the single-mode laser diode. The optical output of the laser diode is a multi-longitudinal mode spectrum spanning 1.98-2.00 μm at an output power of 50 mW CW. The characteristic temperature of the laser diode is 48 K     

Transfer-matrix dynamic model of partly gain-coupled 1.55 μm DFBlasers with a strained-layer MQW active grating

A dynamic model for partly gain-coupled 1.55 μm MQW DFB lasers consisting of etched strained-layer multiquantum wells is presented. For the modulation and noise characteristics of DFB lasers, analytical expressions which take into account both the longitudinal distribution of laser parameters and carrier transport effects are derived for the first time using the transfer-matrix method. As a numerical example, the relaxation oscillation frequency is compared to experimental results, and reasonable agreements are obtained between the theory and experiment     

Generation of frequency-tunable light and frequency reference gridsusing diode lasers for one-petahertz optical frequency sweep generator

Generation of frequency-tunable light and frequency reference grids in a wide frequency span for a diode laser based optical frequency sweep generator has been performed. Frequency tuning and noise characteristics in nonlinear frequency conversions have been discussed. By using AlGaAs, InGaAsP lasers and their frequency conversions in the type II angle phase-matching KTP crystal, highly coherent frequency-tunable outputs have been obtained from 600 THz (0.5 μm) to 170 THz (1.7 μm). Use of the DFB lasers ensures the continuous tuning with a frequency range as wide as 1 THz. Atomic potassium and molecular iodine absorption resonances have been employed as frequency references for stabilizing the frequencies of lasers and the generated light with the frequency stability of 10^-9-10^-10. Optical frequency comb generation has been realized at the 0.8 μm wavelength with a two-sided sidebands span of 4 THz. We have also proposed and demonstrated specific frequency-tunable systems based on sum and difference-generations of diode lasers     

Theoretical analysis of temperature sensitivity of differentialgain in 1.55-μm InGaAsP-InP quantum-well lasers

We study the temperature sensitivity of the differential gain in InGaAsP-InP strained-layer (SL) quantum-well (QW) lasers operating at a wavelength of 1.55 μm. Electrostatic deformation in conduction-band and valence-band profiles is taken into account by solving Poisson's equation and the effective-mass equations for conduction and valence bands in a self-consistent manner. We demonstrate that electrostatic deformation in both band profiles plays a significant role in determining the temperature sensitivity of the differential gain in 1.55-μm InGaAsP-InP SL QW lasers. The physical mechanism for limiting the differential gain at elevated temperatures is also discussed     

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     

High-power, high-temperature InGaAs-AlGaAs strained-layerquantum-well diode lasers

Output power of 2.26 W and maximum power conversion efficiency of 57% were obtained for InGaAs-AlGaAs strained-layer quantum-well lasers (25°C, λ≃1 μm). Output powers were 2.35 W (-55°C) and 1.79 W (75°C) with maximum power efficiencies of 51% (-55°C) and 46% (75°C)     

0.3 W CW single-spatial-mode operation from large-core ARROW-type diode lasers

Large-core-width (6 mu m) antiresonant reflecting optical waveguide (ARROW)-type diode lasers are demonstrated for the first time. The structures have strong intermodal discrimination with low loss for the fundamental mode. As a result, stable, single-spatial-mode operation under CW conditions is obtained up to 300 mW output power at an emission wavelength of 0.98 mu m from strained-layer InGaAs-AlGaAs devices.<>     

Design of a 1.65-μm-band optical time-domain reflectometer

The design and performance of a 1.65-μm-band single-mode optical time-domain reflectometer (OTDR) with a laser diode source are described. The approach employs a high-power laser diode with a strained-layer InGaAs/InGaAsP multiple-quantum-well (MQW) structure which is grown by metalorganic vapor phase epitaxy (MOVPE), an InGaAs avalanche photodiode, and methods for reducing the optical wiring loss in an optical unit. A 1.65-μm-band OTDR is realized with a single-way dynamic range of 25 dB at a pulse width of 1.0 μs