W. Susaki

Low threshold InGaAsP/InP buried crescent laser with double current confinement structure

An InGaAsP/InP laser diode emitting at 1.3 μm with a crescent shaped active region is described. The active region is completely embedded in InP by a two-step LPE technique, and a double current confinement scheme is incorporated with two reverse biased p-n junctions at both sides of the active layer. A threshold current as low as 20 mA has been achieved in CW operation at room temperature. Fundamental transverse mode operation with linear light output-current characteristics and single longitudinal mode oscillation have been obtained.

InGaAsP/InP buried crescent laser diode emitting at 1.3 µm wavelength

The fabrication procedure, designing of an active region and a p-n-p-n current blocking structure, characteristics and the aging results of an InGaAsP/InP buried crescent (BC) laser diode are described. The BC laser diodes exhibit high laser performances, such as a low-threshold current, a fundamental transverse mode oscillation with linear light output-current characteristics. CW operation at as high as 100°C is achieved with a junction up configuration as a result of the improvement in the current blocking structure. A stable CW operation at 80°C has been realized with a constant optical output power of 5 mW.

A very narrow-beam AlGaAs laser with a thin tapered-thickness active layer (T 3 laser)

A very narrow-beam and high-power laser which has a thin tapered-thickness active layer is developed. The property of LPE on a ridged substrate is utilized to obtain the thin tapered-thickness active layer. In the T3laser, the active layer is thinner near the mirror than in the inner region. The main feature of the T3laser is the independent control of the beam divergence perpendicular to the junction ( \theta_{\perp} ) and the threshold current ( Ith ). That is, the narrow beam is obtained with little increase of Ith . Thus \theta_{\perp} as narrow as 10° has been obtained with Ith about 60 mA. The large near-field spot size of the laser is also suitable for high-power operation. The maximum output power of 120 mW in the fundamental transverse mode has been realized for a laser emitting at 780 nm. Stable 30 mW operation at 50°C has been confirmed over 7000 h.

High-power 780 nm window diffusion stripe laser diodes fabricated by an open-tube two-step diffusion technique

High-power and low-threshold-current GaAlAs lasers with a simple window structure fabricated by controllable open-tube two-step diffusion and single-step metalorganic chemical vapor deposition are discussed. The window structure and the waveguide with a narrow width around 2 mu m are formed by diffusion of zinc, which just passes through an n-type active layer. CW output power up to 134 mW without catastrophic damage and a threshold current of 17 mA have been achieved. A maximum output power density of 16 MW/cm/sup 2/ is estimated. A stable fundamental transverse mode of up to 100 mV in the wavelength range of 780 nm is obtained. Excellent uniformity of device characteristics is confirmed. >

Spontaneous emission behavior in AlGaAs TJS lasers

Spontaneous emission in the direction perpendicular to the lasing direction is experimentally examined in AlGaAs TJS lasers which lase in the fundamental transverse and single longitudinal mode. It is found that the spontaneous emission intensity uniformly saturates above threshold, spatially as well as spectrally. Spontaneous emission peak energy is compared to the lasing energy in a series of lasers with a different Al content in the active region. The energy difference between two energies is shown to be 50 meV and to be independent of the Al content from 0 to 0.26. The absorption coefficient in the active region is calculated from the spontaneous emission spectral shape, which is reasonably explained with the doping condition of the TJS lasers.

High output power and high temperature operation of 1.5 mu m DFB-PPIBH laser diodes

Highly efficient 1.5- mu m distributed-feedback (DFB) p-substrate partially-inverted buried heterostructure laser diodes with a thin active layer developed using a metal-organic chemical vapor deposition technique are discussed. An average slope efficiency of 0.26 mW/mA (quantum efficiency 33%) and maximum slope efficiency of 0.39 mW MW/mA (49%) were achieved. The full width at half maximum in the direction perpendicular to the junction plane of 25 degrees was obtained. A high output power of 77 mW was obtained under CW conditions at room temperature. This laser diode lased up to 120 degrees C, and more than 10 mW was obtained, even at 90 degrees C. >

Transverse mode control in wide-single-stripe lasers by loading modal filters

Preliminary studies demonstrate the effectiveness of modal filters for controlling transverse modes in wide-single-stripe SBA (self-aligned bent-active-layer) lasers by means of two methods. The first uses a flared waveguide SBA laser while the other uses a wide-stripe SBA laser with a modal reflector at the output facet. Both lasers demonstrate single-lobed far-field patterns. These preliminary experiments show that both modal filters are effective for transverse-mode control. Higher output power in the fundamental transverse mode can be attained by combining these two modal filters.<<ETX>>

Lateral mode controlled wide stripe SBA lasers by modal reflector

Wide stripe SBA lasers with modal reflector have been developed. Extremely narrow single-lobed far-field patterns for the lateral direction are observed up to 0.3 W under CW (continuous-wave) conditions and 0.4 W under pulsed conditions. A simple theoretical model for describing the mode profile is calculated with the model. Good agreement between experimental and calculated far-field patterns is obtained.<<ETX>>

High temperature and long life operation of new InGaAsP/InP 1.3 &#181;m buried crescent lasers

The main purpose of this study is to realize a highly reliable InP/InGaAsP lasers even at elevated temperatures. We present and demonstrate a new BC structure (displaced BC, D-BC) with optimized device parameters such as the dimensions of the active region and the doping levels of the constituent layers. A stable long life operation for more than 4,000 hours in automatic power control (APC) mode operation at a temperature of 80° C is obtained in these new lasers. The life time of the lasers are estimated to be8 \times 10^{4}hours( ≃ 9 years).