Reliable 1-W CW operation of high-brightness tapered diode lasers at 735 nm

The long-term stability of high-brightness diode lasers at 735 nm was investigated. The diodes consist of an index-guided straight section and a gain-guided tapered section. A 1-W continuous-wave operation for 2-mm-long tapered lasers over 3200 h is reported. The experiments demonstrate high reliability with degradation rates below 3.2/spl times/10/sup -5/ h/sup -1/.     

Performance characteristics of high-brightness, CW, diode laser arrays

Recently developed, high-brightness diode laser arrays have been tested at 50°C at output powers of 0.5 W CW and 1.0W CW from 100?m- and 200?m-wide active regions, respectively. The extrapolated lifetimes at room temperature exceed 40000 h. The maximum CW power output prior to catastrophic degradation of the facets is 2.0 W for the 100?m device and greater than 3 W for the 200?m-aperture device.     

Monolithically-integrated hybrid heterostructure diode laser with dielectric-film waveguide DBR

In the monolithically-integrated hybrid (MIH) DBR diode laser, the five-layer Ga(Al)As-GaAs heterostructure waveguide of the gain region was monolithically butt-joined on a common GaAs substrate with a highly-transparent corrugated dielectric-film waveguide consisting of sputtered SiO2, Ta2O5, and evaporated (corrugated) As2S3layers. The laser operated with the first-order grating under the pulsed current pumping at 300 K. The efficient resonant mode conversion (70 percent in power) has been obtained at the interface between the heterostructure and dielectric waveguides. The fundamental transverse and single-longitudinal mode output emission was obtained up to 160 mW (Ith = 120mA) with external differential quantum efficiencyeta simeq 32percent. The advantages of a dielectric-film waveguide DBR are demonstrated. The use of such a DBR results in a high degree of sidemode suppression and stability of the spectral position of the emission line under the temperature variation, the corresponding spectral shift beinglsim 0.01Å/K.     

Continuously tunable single-frequency laser diode utilising transverse tuning scheme

A new wavelength-tunable single-frequency lase diode has been developed using a tunable twin-guide structure. The applied transverse tuning scheme provides a basically continuous tuning behaviour with only a single wavelength control current. The first 400 mu m-long, lambda =1.56 mu m devices are tunable over a range of 1.5 nm and show the expected continuous tuning behaviour.<>     

25-W CW high-brightness tapered semiconductor laser-array

High-power high-brightness laser diode arrays comprising 25 tapered laser oscillators have been fabricated. The devices, based on recently developed low-modal gain epitaxial layer-structures, deliver a maximum output power of more than 25-W continuous-wave. A high beam quality uniformity is achieved with an average beam quality factor of M ²=2.6 for each individual emitter. Compared to conventional broad-area laser diode arrays the brightness of each emitter is improved by more than an order of magnitude in the slow-axis direction. These arrays have the potential to produce optical power densities as high as 1 MW/cm²     

2.0 W CW, diffraction-limited tapered amplifier with diode injection

The authors have demonstrated an all-semiconductor discrete-element 1.5 mm length tapered-amplifier MOPA (master oscillator power amplifier) emitting up to 2.0 W CW in a diffraction-limited pattern. The tapered single-pass amplifier MOPA exhibits a very high differential efficiency of 72% and a total energy conversion efficiency of 39% at 2.0 W CW output power. The high efficiency of the MOPA is attributed to the tapered amplifier design, which maximises extraction efficiency with a low-power injected beam of 25 mW from a single-mode laser diode. Such an MOPA will have applications where compact, high-efficiency, diffraction-limited sources of radiation are required, such as frequency doubling and free-space communication.<>     

Multielectrode DBR laser diode for wide bandwidth and flat FM response

A flat red-shifted FM response over a 1 GHz bandwidth has been achieved in a newly fabricated three-electrode DBR LD. Since the DBR structure makes it possible to tune the wavelength without distorting the FM characteristics, the LD is suitable for transmitters in optical FDM communications using FSK lightwaves.<>     

Pure frequency modulation of a multielectrodedistributed-Bragg-reflector (DBR) laser diode

Intensity-modulation suppressed frequency modulation (FM) is demonstrated over a 600-MHz bandwidth by using a three-electrode distributed-Bragg-reflector (DBR) laser diode (LD). A nonuniform carrier-density distribution in the active region is realized by two separated electrodes, whose push-pull modulation yields only a 0.7% intensity fluctuation per 1-GHz frequency deviation. This corresponds to a 20-dB FM purity improvement. A third electrode on the DBR region makes it possible to tune the wavelength simultaneously. Because of its wider modulation bandwidth, the LD is suitable for the lightwave oscillator in frequency-shift-keyed (FSK) transmissions and for linewidth reduction by electrical feedback     

Quasi-3-D simulation of high-brightness tapered lasers

We present a simulation tool useful to optimize the design of semiconductor tapered lasers and to study the physical processes inside of them. This is achieved by using a state-of-the-art quasi-three-dimensional (quasi-3-D) electrical and thermal model, coupled to a two-dimensional (2-D) wide-angle beam propagation method optical model. A calibration procedure of model parameters is proposed to contribute to the development of reliable simulation tools. Different laser diodes with a tapered gain section, emitting at 735 and 975 nm, are used to validate the model through the extensive comparison of experimental and simulated results. The suitability of 2-D and 3-D electrical, thermal, and optical models is discussed in terms accuracy and computational effort.     

High-power high-brightness GaInAsSb-AlGaAsSb tapered laser arrayswith anamorphic collimating lenses emitting at 2.05 μm

Linear arrays of GaInAsSb-AlGaAsSb tapered MQW lasers emitting at 2.05 μm have been fabricated and operated with 1-ms current pulses. Peak power over 3 W was obtained for nine-element arrays at 18.5 A. Up to 1.7-W peak power, within a 65-mrad full-angle cone, was measured in the far field using anamorphic collimating lens arrays, fabricated by mass transport in GaP     

11 W quasi-CW monolithic laser diode arrays

An optical power of 11 W from one facet has been obtained from a 1 cm integrated GaAlAs laser array for 150 ?s is pulse widths (quasi-CW operation). The array consists of 20 tenstripe lasers spaced along the bar, employing about 20% of the facet length for active laser emission.     

Picosecond laser diode pulse amplification up to 12 W by laserdiode pumped erbium-doped fiber

Intense picosecond optical pulse generation from a gain-switched laser diode (LD) was demonstrated using a 1.48-μm LD-pumped Er³⁺ -doped fiber laser amplifier. Saturation characteristics of the amplifier output power were also measured as a function of input repetition frequency. An amplified peak power of 12 W and 105-pJ pulse energy were obtained for 9-ps pulses at a 33-GHz repetition frequency. This is the highest peak power yet demonstrated in pulse generation employing all-laser diodes as active devices     

具有楔形多模干涉波导结构的大功率半导体激光器的研究

设计并制作了一种具有两段楔形（Taper）多模干涉波导（Multimode Interferometer Waveguide,MMI）级联的大功率半导体激光器。利用3D束传播算法（Beam Propagation Method,BPM）,模拟计算了光场在楔形多模干涉波导的传播和损耗,设计出器件的最佳尺寸。激光器材料采用小应变InGaAs/InGaAsP多量子阱有源区加InGaAsP（1.2Q）限制层的三明治结构,器件的制作则采用传统的F-P激光器的制作工艺。在25℃,加连续电流条件下,激光器的饱和输出功率达到32mW,饱和电流达到600mA,并实现稳定的单横模输出。相比于单脊窄条的F-P激光器（饱和输出功率9.8mW）、相同长度的矩形MMI级联的激光器（饱和输出功率21.8mW）,由于具有更大的有源区,楔形MMI级联的激光器具有较大的饱和输出功率、较小的电阻等特点。     

A high-power tapered and cascaded active multimode interferometer semiconductor laser diode

A high power semiconductor laser diode with a tapered and cascaded active multimode interferometer (MMI) cavity was designed and demonstrated.An output power as high as 32 mW was obtained for the novel laser diode with a tapered and cascaded active MMI cavity,being much higher than the 9.8 mW output power of the conventional single ridge F-P laser with the same material structure and the same device length due to the larger active area;and also being higher than the 21.2 mW output power of the rectangular and cascaded active MMI laser diode with nearly the same structure,except for the shape of the MMI area.In addition,the tapered and cascaded active multimode interferometer laser showed stable single mode outputs up to the maximum output power.     

100 W 671 nm visible laser diode array

A GaInP/AlGaInP, strained-layer, single quantum well, monolithic laser diode array is described which has achieved a room temperature quasi-CW (100 mu s, 10 Hz) output of over 100 W at 671 nm.<>     

15 W CW monolithic AlGaAs laser diode arrays

Good continuous-wave lifetimes have been demonstrated for 1 cm wide monolithic AlGaAs laser diode arrays with a 3500 mu m total aperture width at a power level of 15 W. This represents the highest CW power level at which long lifetimes have been obtained.<>     

Dual-wavelength DBR fiber laser

Stable continuous-wave lasing of two longitudinal modes of a distributed Bragg reflector fiber laser is reported. Intensity noise and coupling between the modes was characterized for both 0.8- and 0.2-nm mode separations.     

11.5 W pulsed operation of antiguided laser diode array

A 40-stripe array of antiguided laser diodes is operated to a pulsed output power of 11.5 W. At the output power of 11.5 W, the full width at half maximum of the central lobe of the in-phase far fields is 1 degrees .<>     

Multiple laser diode array pumped Cs laser with 48W output power

A Cs vapour laser that utilises four laser diode arrays for longitudinal pumping of the gain medium is demonstrated. A maximum output power of 48 W was achieved with a total optical to optical efficiency of 49% and a slope efficiency of 52%. This work shows that the diode pumped alkali lasers can be scaled to higher powers.     

High-brightness 735 nm tapered diode lasers

High brightness 735 nm single emitter tapered diode lasers were manufactured and analysed. A beam propagation factor M² smaller than 1.4 is achieved up to an output power of 2 W