Narrow spectral linewidth 150 mW semiconductor laser with fundamental transverse mode for SHG light source

A highly reliable, narrow spectral linewidth, 150 mW high-power semiconductor laser that oscillates at a wavelength of 860 nm has been developed, by optimising the structure with a 0.7 mu m thick p-cladding layer, a 900 mu m long cavity length, and current-blocking regions near the facets. Stable, fundamental transverse mode operation was obtained up to 230 mW. The spectral linewidth was 5 MHz at 150 mW. stable operation under 150 mW at 50 degrees C was confirmed for more than 2000 h.<>     

Amplification properties of a tunable single transverse mode laser diode

The amplification properties of a tunable single transverse mode laser diode can be exploited to be used as ann times 1wavelength division switch. This kind of switch is expected to play an important role in telecommunications systems, especially when signals are not synchronous or when signal bit rates are various. The light amplification ratio between a desired main-mode wavelength and undesired submode wavelengths are improved by decreasing injection light power, and a ratio of 8.5 dB is achieved. This experimental result is in good agreement with theory. It is predicted theoretically using rate equations that the ratio is also improved by increasing the laser cavity mirror loss difference between the main mode and the submodes. A light amplification ratio of more than 11 dB is obtained when the cavity mirror loss difference is more than 50 cm^-1.     

Toshiba's 200mW blue-violet laser on view

On exhibition at CEATEC Japan 2003 at Makuhari Messe, Chiba prefecture, was Toshiba Corp’s gallium-nitride based blue-violet laser offering high optical output of 200mW, while claiming the lowest noise characteristics ever attained.Visit www.three-fives.com for the latest advanced semiconductor industry news     

AlGaAs transverse junction stripe laser with distributed Bragg reflector

A new longitudinal mode stabilised AlGaAs transverse junction stripe laser with distributed Bragg reflector has been fabricated. Stabilised single longitudinal mode operation was obtained; temperature dependence of the lasing wavelength for the d.b.r. t.j.s. laser was 0.5 ?/°C.     

Interference of an AlGaAs laser diode using a 4.15 km single mode fiber cable

Polarization characteristics in cabled single mode fibers were studied. By using 4.15 km long fibers and a single frequency AlGaAs double-heterostructure laser, interference fringes were observed.     

Anomalous tuning of single mode AlGaAs diode lasers

Deviations from the normal tuning of a TJS AlGaAs diode laser have been observed. In the usual situation, the emitted wavelength of a single mode diode laser as a function of temperature is described by a "staircase" function, that is, the tuning curve consists of regions of smoothly increasing wavelength as a function of temperature separated by positive wavelength mode hops. We have observed a tuning curve for which the regions of smooth temperature tuning are separated by negative wavelength mode hops. It is suggested that this effect is due to the existence of structure in the laser's effective gain curve.     

GaAlAs window lasers emitting 500 mW CW in fundamental mode

Single element GaAlAs lasers using the buried heterostructure geometry with tapered waveguides and incorporating nonabsorbing facets have been fabricated. Metalorganic chemical vapour phase deposition was used for the double heterostructure first growth, and liquid phase epitaxy was used for the current confining and nonabsorbing facet second growth. 500 mW CW in single spatial mode emission was obtained from devices with 1 mm long cavities.<>     

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.<>     

Thermally accelerated life testing of single mode, double-heterostructure, AlGaAs laser diodes operated pulsed at 50mW peak power

Single spatial mode, double-heterostructure, channel-substrate-planar AlGaAs laser diodes have been life tested under thermally accelerated conditions to characterize the reliability of the diodes in a digital, optical communication system intended for space application. The diodes were operated pulsed under constant drive current conditions at 50 mW peak power, 25 ns pulse width, and 1 percent duty cycle in a dry, inert environment at ambient test temperatures at 40,55, and 70°C. Diode performance parameters as related to the space application, such as pulsewidth, peak power, wavelength spectrum, spatial mode, and threshold current, were periodically monitored. Tests have continued for over 14 000 h. The test results for all diodes with failure defined by power degradation alone is compared to the test results for single mode diodes with failure defined by power degradation, wavelength shift and spatial mode changes. It is found that the life test results are substantially equivalent but differ from earlier published reports for laser diodes operated CW. An activation energy of about 0.39 eV is deduced with a predicted median life of about5 times 10^{4}h at 20 °C. These values are somewhat lower than those found for diodes operated CW and are attributed to the use of single mode laser diodes here. It is concluded that thermally accelerated life testing for single spatial mode laser diodes must incorporate a means to separate bulk material, current, and optical density induced degradation effects. A test scheme is proposed.     

Film-level hybrid integration of AlGaAs laser diode with glasswaveguide on Si substrate

A ridge-waveguide AlGaAs laser diode (LD) was integrated with a SiO₂-Ta₂O₅ embedded waveguide on a Si substrate by using a film-level hybrid integration technique of semiconductor epitaxial film. CW operation of the LD was achieved at room temperature. The LD-waveguide butt-coupling loss was 9 dB, and the loss due to misalignment was estimated at 3 dB, which corresponds to a displacement of about 1 μm in both the vertical and lateral directions     

Single transverse mode 850nm GaAs/AlGaAs lasers with narrow beam divergence

GaAs/AlGaAs 850 nm range lasers based on a longitudinal photonic bandgap crystal waveguide show narrow vertical far-field pattern. Vertical and lateral beam divergence with FWHM below 10deg and 5deg, respectively, is demonstrated for 4 mum stripe width, being independent on injection current. Excellent beam quality with M² =1.4, low internal losses of 1.4 cm^-1 and high differential quantum efficiency of 83% are observed     

Highly reliable high-power 980-nm pump laser

We report on highly reliable, high-power, and high-performance 980-nm quantum-well laser chips and modules. Ridge waveguide laser diode chips with 750-mW output power and 500-mW fiber Bragg grating stabilized modules have been achieved and Telcordia-qualified. Long-term reliability tests show a very low failure rate of 400 FIT (failures in time) at 900-mA operating current or 500-mW module power. The kink-free fiber coupled module output power can be as high as 640 mW with grating stabilization, which produces very good wavelength stability and power stability. A further improved structure shows a record continuous-wave rollover chip power of 1.6 W for the 5-/spl mu/m-wide ridge waveguide laser diodes.     

Transverse junction buried heterostructure (TJ-BH) AlGaAs diode laser

A successful demonstration of a transverse junction buried heterostructure AlGaAs diode laser is described. A typical threshold current of 40mA and a typical differential efficiency of 50% is obtained for the 1.5?m-wide active region and the 250?m-long diode.     

High-power transverse micro-stack weakly coupled laser diode bars

Transverse micro-stack semiconductor laser bars are put forward to improve the output optical power of semiconductor laser bars at low injection current. Micro-stack tunnel regeneration tri-active region laser structure was grown by metal organic chemical vapor deposition (MOCVD) and laser diode bars with 50% fill factors were fabricated. Experiments show that the insulated recesses strongly affect the properties of the bars. When the recess depth is less than 1.13 μm, the bars do not work well. By optimizing the insulated recess depth, threshold current can be reduced to 7.05 A, the optical power exceeds 79 W under 50 A driving current and the slope efficiency reaches 1.81 W/A.     

450 Hz relative frequency stability in an AlGaAs diode laser

A commercial AlGaAs diode laser is frequency-locked to a Fabry-Perot interferometer. The temperature stabilisation loop of the diode laser system maintains the relative stability within 11 kHz. When the frequency control loop is closed, the relative frequency stability is improved to 450 Hz.     

Fractional spontaneous emission coupled into AlGaAs laser mode

Spontaneous-emission power coupled into laser modes in AlGaAs double-heterostructure lasers is evaluated experimentally. The power fraction is proportional to V?1.5.     

Inner-stripe AlGaAs/GaAs laser diode by single-step molecular beam epitaxy

A novel fabrication technique for a real refractive-index-guide inner-stripe laser by a single-step crystal growth is reported. The injected current is confined in the p-type silicon-doped GaAs region on the V-shaped groove with (111)A slopes by the crystal-orientation-dependent amphoteric nature of the silicon impurity in GaAs.     

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.<>     

Picosecond internal Q-switching mode correlates with laser diode breakdown voltage

The record picosecond power density recently achieved with a current-pumped laser diode turned our attention to a still unexplained 50-year-old phenomenon termed “internal Q-switching”. The correlation found experimentally here between the relatively high breakdown voltage (～5–11 V) in a heavily doped single-heterostructure laser diode and its high-power picosecond lasing provides a means for solving the puzzle. Together with the experimental fact that picosecond lasing occurs from the p-n junction, this implies that internal Q-switching is determined by the compensated layer rather than by “traditional” single-heterostructure waveguide. This finding is valid for various growth technologies independently of whether the high break-down voltage and picosecond lasing are achieved by exact compensation of shallow donors by shallow acceptors, or by doping profile gradients.     

High-efficiency AlGaAs-based laser diode at 808 nm with large transverse spot size

Lasers diodes having a large transverse spot size have been fabricated from a modified graded index separate confinement heterostructure with an active region consisting of two 70 /spl Aring/ Al/sub 0.15/In/sub 0.10/Ga/sub 0.75/As strained quantum wells. The catastrophic optical damage threshold for these large transverse mode devices is increased by more than two times over that of conventional devices while still maintaining good device performance.