High-power ridge waveguide InGaAsN lasers fabricated with pulsed anodic oxidation

High-power InGaAsN triple-quantum-well strain-compensated lasers grown by metal-organic chemical vapor deposition were fabricated with pulsed anodic oxidation. A maximum light power output of 145 mW was obtained from a 4-/spl mu/m ridge waveguide uncoated laser diode in continuous-wave (CW) mode at room temperature. The devices operated in CW mode up to 130/spl deg/C with a characteristic temperature of 138 K in range of 20/spl deg/C-90/spl deg/C.     

High-power 2.3-/spl mu/m GaSb-based linear laser array

High-power 2.3-/spl mu/m In(Al)GaAsSb-GaSb type-I double quantum-well diode laser arrays were fabricated and characterized. Linear laser arrays with 19 100-/spl mu/m-wide elements on a 1-cm-long bar generated 10 W in continuous-wave (CW) mode and 18.5 W in quasi-CW mode (30 /spl mu/s/300 Hz) at a heatsink temperature of 18/spl deg/C. Array power conversion efficiency peaked at 30 A and was about 9%. Device internal efficiency was about 50%. Individual laser differential gain with respect to current was about twice as high as in InP-based laser heterostructures, demonstrating the potential of GaSb-based material system for high-power CW room-temperature laser diode arrays.     

Lasing emission of InGaAs quantum dot microdisk diodes

An improved three-arm airbridge contacted microdisk diode structure is presented. Continuous-wave lasing from InGaAs quantum dot (QD) in a /spl sim/4-/spl mu/m-diameter microdisks is reported with the threshold current /spl sim/40 /spl mu/A at T=5 K. With the increase of injection current, the QD's emission blueshifts due to the band-filling effect, while the laser mode peak redshifts by thermal effect. When the QD's gain spectra shift out of alignment with the lasing mode, the next available whispering gallery mode starts lasing from QD wetting layer. The thermal heating effect is discussed by investigating the modes redshift with respect to injection current.     

High-power 2.3 /spl mu/m laser arrays emitting 10 W CW at room temperature

High-power 2.3 /spl mu/m In(Al)GaAsSb/GaSb type-I double quantum-well diode laser arrays have been fabricated and characterised. Linear laser arrays with 19 100 /spl mu/m-wide elements on a 1 cm-long bar generated 10 W in continuous-wave (CW) mode and 18.5 W in quasi-CW mode (30 /spl mu/s/300 Hz) at a heatsink temperature of 18/spl deg/C.     

External cavity laser sensor using synchronously-pumped laser diode for position measurements of rough surfaces

A novel optical sensor for absolute position measurements of rough surfaces is presented. The technical surface acts as reflector of an external cavity for an antireflection-coated laser diode. Evaluation of the resulting mode spacing determines the laser cavity length, i.e. the distance to the rough surface. Modelocking by synchronous pumping of the laser diode allows highly-resolved measurements with position resolution of 5 /spl mu/m and temporal resolution of 200 /spl mu/s.     

Highly coherent electronically tunable waveguide extended cavity diode laser

A frequency agile extended cavity diode laser using an integrated Bragg reflector in a Ti : Fe : LiNbO/sub 3/ waveguide is developed and characterized. The laser emits up to 7 mW in the 1.5-/spl mu/m telecommunication window. The emission spectrum exhibits a 18-kHz linewidth, >40-dB sidemode suppression ratio, and a wavelength stability of /spl plusmn/1 pm over hours. Very fast mode hop-free frequency tuning is achieved through the electrooptic effect, with a tuning slope of 55.5 MHz/V.     

Optical mode converter integration with InP-InGaAsP active and passive waveguides using a single regrowth process

A new method for integration of optical mode converters with InP-based photonic integrated circuits is described and demonstrated. The mode converter is integrated to a Sampled Grating DBR (SG-DBR) laser to demonstrate integration and to facilitate accurate fiber-coupling loss measurements. The entire fabrication process requires a single MOCVD regrowth, making it compatible with low-cost integration with other photonic components. The mode converter utilizes a vertically tapered geometry and yields a record 86% coupling efficiency using a lensed, uncoated, single-mode fiber. Cleaved fiber to InP-based waveguide coupling loss sensitivity is measured to be better than 1 dB with /spl plusmn/ 1.85-/spl mu/m lateral fiber misalignment and /spl plusmn/1.5-/spl mu/m transversal fiber misalignment.     

High-performance singlemode InGaNAs/GaAs laser

Performance characteristics of an InGaNAs/GaAs ridge-waveguide in-plane laser diode, which is grown by molecular beam epitaxy, are reported. The laser emits at a wavelength of 1.262 /spl mu/m in a single lateral mode, launching an output up to 240 mW at 20/spl deg/C and 20 mW at 120/spl deg/C. The threshold is 15 mA at 20/spl deg/C, corresponding to a threshold current density of 313 A/cm/sup 2/.     

Asymmetric broad waveguide diode lasers (/spl lambda/ = 980 nm) of large equivalent transverse spot size and low temperature sensitivity

980-nm InGaAs-InGaAsP diode lasers of asymmetric broad-waveguide (BW) transverse structure are demonstrated. Single-transverse-mode devices have equivalent (transverse) spot sizes of 0.8 /spl mu/m (i.e., significantly larger than for symmetric BW structures), which are obtained at no price in device-parameter temperature sensitivity. Built-in discrimination against the first-order transverse mode allows fundamental-transverse-mode operation in relatively narrow beams (/spl theta//sub /spl perp// = 34/spl deg/). For 2-mm-long 100-/spl mu/m-wide-stripe uncoated devices with double-quantum-well active regions, the threshold-current density is as low as 190 A/cm/sup 2/, while the characteristic temperatures for the threshold-current density T/sub 0/, and the external differential quantum efficiency T/sub 1/ are high: 183 K and 650 K, respectively.     

Two-step laterally tapered spot-size converter 1.55-/spl mu/m DFB laser diode having a high slope efficiency

We demonstrate a two-step lateral tapered 1.55-/spl mu/m spot-size converter distributed feedback laser diode (SSC DFB LD) having slope efficiencies as high as 0.457 and 0.319 mW/mA measured at 25 /spl deg/C and 85 /spl deg/C, respectively. The SSC DFB LD fabricated by using a nonselective grating process has a double core waveguide structure including a planar buried heterostructure type active waveguide and a ridge type passive waveguide. The fabricated SSC DFB LD operates at 1.553-/spl mu/m wavelength and shows a far-field pattern in horizontal and vertical directions of 7.3/spl deg/ and 11.6/spl deg/, respectively.     

1.55-/spl mu/m spot-size converter integrated laser diode with conventional buried-heterostructure laser process

A 1.55-/spl mu/m spot-size converter integrated laser diode is demonstrated with conventional buried-heterostructure laser process. For the spot-size converter, we employed a double-waveguide structure in which a ridge-based passive waveguide was incorporated. The passive waveguide was optically combined with a laterally tapered active waveguide to control mode size. The threshold current was measured to be 5 mA together with high slope efficiency of 0.45 W/A. The beam divergence angles in the horizontal and vertical directions were as small as 9.0/spl deg/ and 7.8/spl deg/, respectively.     

High-power highly reliable 1.02-1.06-/spl mu/m InGaAs strained-quantum-well laser diodes

By growing the InGaAs active layer at temperatures lower than in conventional growth, we extended the lasing wavelength and presented the high reliability in InGaAs strained-quantum-well laser diodes. Equivalent I-L characteristics were obtained for 1.02-, 1.05-, and 1.06-/spl mu/m laser diodes with a cavity length of 1200 /spl mu/m. Maximum output power as high as 800 mW and fundamental transverse mode operation at up to 400 mW were obtained at 1.06 /spl mu/m and an 1800-/spl mu/m cavity. Stable operation was observed for over 14 000 h under auto-power-control of 225 mW at 50/spl deg/C for the 1.02-, 1.05-, and 1.06-/spl mu/m lasers with a 900-/spl mu/m cavity.     

Low-chirp and high-power 1.55-/spl mu/m strained-quantum-well complex-coupled DFB laser

High-power, low-chirp, and low-threshold current characteristics of 1.55 /spl mu/m complex-coupled compressively strained InGaAsP quantum-well DFB laser with a loss grating are presented. Kink-free light-current characteristics with single-mode power over 40 mW are demonstrated for uncoated devices. A relatively low threshold current of 10 mA and a high slope efficiency of 0.23 W/A have been obtained even with the loss grating employed. Stable single-mode emission was demonstrated with a side mode suppression ratio up to 54 dB, a low chirp of less than 0.3 nm under 1 Gb/s pseudorandom digital modulation and a spectral linewidth of 8 MHz.     

Bidirectional, subcarrier-multiplexed transmission using 1.3-/spl mu/m Fabry-Perot lasers

We demonstrate a full-duplex, subcarrier-multiplexed, transmission system which employs 1.3-/spl mu/m Fabry-Perot strained layer MQW laser diode transmitters in both directions. Coherent effects are reduced by using lasers with different mode spacing.     

Simple planar structure for high-performance AlInAs avalanche photodiodes

We demonstrate a high-performance AlInAs avalanche photodiode (APD) based on a novel planar diode concept. The APD features a simple planar structure without a guardring, which simplifies production making it more like a PIN photodiode process. Measured device characteristics designed for 10-Gb/s use were a dark current of 0.16 /spl mu/A, responsivity of 0.88 A/W, and a gain-bandwidth product of 120 GHz. Reliability was guaranteed by an aging test exceeding 2400 h, whose conditions were a reverse dark current of 100 /spl mu/A at 175/spl deg/C. These features and performance indicate that the AlInAs APD is highly practical.     

InAsSbP-InAsSb-InAs diode lasers emitting at 3.2 /spl mu/m grown by metal-organic chemical vapor deposition

InAsSb-InAsSbP double heterostructure diode lasers have been grown by metal-organic chemical vapor deposition on (100) InAs substrates. High-output powers of 660 mW in pulse mode and 300 mW in continuous wave operation with 400-/spl mu/m cavity length and 100-/spl mu/m-wide aperture at 78 K have been obtained. These devices showed low threshold current density of 40 A/cm/sup 2/, low internal loss of 3.0 cm/sup -1/, far-field /spl theta//sub /spl perp// of 34/spl deg/ with differential efficiency of 90% at 78 K, and high operating temperatures of 220 K.     

Ytterbium laser with reduced thermal loading

We report a novel design for a high-power ytterbium disk laser. This laser utilizes radial diode pumping of a back surface cooled active-mirror geometry. Wing absorption of the pump light at 0.99 /spl mu/m allows efficient laser operation at 1.05 /spl mu/m with a low quantum defect. Laser performance and thermal loading were characterized for a wide range of conditions. Optimized operation of the laser yielded 490 W in a quasi-continuous-wave mode. Electrical efficiency of the laser was found to be 9.4%, while heating of the laser disk was only 3.2% of the absorbed optical power. Fluorescence re-absorption is identified as the principal heat generation mechanism in this laser. A simplified extension to the conventional rate model is proposed for lasing in radiation-trapped systems. This model allows power flow calculations in a radiation-trapped laser system using a single parameter determined from fluorescence decay waveforms. The revised model agrees with heat load measurements.     

A two-step laterally tapered 1.55-/spl mu/m SSC DFB laser fabricated by using a nonselective grating process

We demonstrate a two-step laterally tapered 1.55-/spl mu/m spot size converter distributed feedback laser diode (SSC DFB LD) having a planar buried heterostructure-type active waveguide and a ridge-type passive waveguide fabricated by using a nonselective grating process. Unlike conventional SSC DFB LDs, where a selective grating is employed, this SSC DFB LD employed a nonselective grating over the entire device region in order to make its fabrication much simpler than that of the conventional SSC DFB LDs. The two-step laterally tapered SSC is effective in removing an unwanted wavelength peak originating from the SSC section having a multiquantum well and a grating under it. The fabricated SSC DFB LD operates at 1.553-/spl mu/m wavelength and shows a far field pattern in horizontal and vertical directions of 13.4/spl deg/ and 19.5/spl deg/, respectively.     

Demonstration of passive Q-switching in multiquantum well InGaAs/AlGaInAs diode laser

The first passive Q-switched operation is reported of an InGaAs-AlGaInAs diode laser with a frequency repetition ranging from 1 to 2.5 GHz at the emitting wavelength of 1.58 /spl mu/m. This material is important as a thermally stable alternative to InGaAsP based laser systems operating around 1.5 /spl mu/m.     

Continuous-wave operation of GaInAsSb-GaSb type-II ridge waveguide lasers emitting at 2.8 /spl mu/m

We have realized compressively strained GaInAsSb-GaSb type-II double quantum-well lasers with an emission wavelength of 2.8 /spl mu/m. Using broad area devices, an internal absorption of 9.8 cm/sup -1/ and an internal quantum efficiency of 0.57 is determined. For the increase of the threshold current with temperature, a T/sub 0/ of 44 K is obtained. Narrow ridge waveguide lasers show continuous-wave laser operation at temperatures up to 45 /spl deg/C, with room-temperature (RT) threshold current of 37 mA. At RT, the maximum optical output power per facet of an uncoated 800/spl times/7 /spl mu/m/sup 2/ ridge waveguide laser exceeds 8 mW.