Lateral Mode Operation Research Articles

Apodizing holographic gratings for the modal control of semiconductor lasers

We first present the fabrication technique of apodizing holographic gratings. Gratings with a spatially variable reflectivity profile were obtained by the interference of two Gaussian beams on a glass plate covered with a photoresist. When the exposure time was short enough to avoid saturation of the photoresist, gratings with a quasi-Gaussian reflectivity profile for the beam reflected in the -1 order were produced; the reflectivity at the center could be as high as 71%, and the half-width of the reflectivity profile at the e(-1) position could be as small as 180 mum. Apodizing gratings were used as the end mirror of the external cavity of a broad-area semiconductor laser. Single longitudinal- and lateral-mode operation was observed over the full range of allowed injection currents.

Highly reliable and stable-lateral-mode operation of high-power 0.98-μm InGaAs-InGaAsP lasers with an exponential-shaped flared stripe

A 0.98-/spl mu/m InGaAs-InGaAsP-GaAs strained quantum-well (QW) laser with an exponential-shaped flared stripe is proposed for high-power, highly reliable operation. The stripe width is wider at the front facet to reduce the optical density by widening the spot size. The stripe width is narrower at the rear facet for stable lateral-mode operation. The stripe width in the transient region is varied exponentially along the cavity for smooth mode transformation. We showed that this structure expands the spot size effectively without any deterioration in stable lateral-mode operation. The kink-occurrence output power is determined only by the stripe width at the rear facet, and the spot size at the front facet is a function only of the stripe width at the front facet. The maximum output power is 40-60% higher than that of ordinary straight-stripe lasers for the same kink-occurrence output power. Testing at 150 mW showed stable operation with an estimated lifetime of more than 200000 h at 25/spl deg/C.

Optimum designs for InGaAsP/InP (λ = 1.3μm) planoconvex waveguide lasers under lasing conditions

Lasing characteristics for 1.3 μm InGaAsP/InP planoconvex waveguide (PCW) lasers were investigated both theoretically and experimentally. Fundamental lateral transverse-mode stability, light-output/ current characteristics, including threshold current and external differential quantum efficiency, and fundamental- mode intensity profiles were investigated up to a high injection-current level by using PCW lasers with individually varying structural design parameters. The experimental results were in good agreement with calculations, which were carried out taking into account carrier outdiffusion along the junction plane and spatial hole burning and their effects on the waveguiding. It was found that a narrow groove width (narrow channel), a relatively large built-in effective refractive index difference and a narrow injection current region width are the main PCW structural design conditions responsible for the high-quality lasing characteristics. The experimental results revealed that high-quality 1.3 μm InGaAsP/InP narrow-channel PCW lasers with 2.5 μm groove width show stable fundamental lateral transverse mode operation up to three times the threshold current, at which 25 m W output power from a facet is attained under CW operation.

Curved junction stabilized filament (CJSF) double-heterostructure injection laser

We have fabricated a new type of channel stripe laser with a curved active region which has a spatially stabilized output for measurements up to 2ITh (Pout=75 mW/facet). The CJSF laser has excellent lateral and longitudinal mode selectivity. The laser operates in almost single longitudinal mode when the current exceeds 1.1ITh. Zeroth-order lateral mode operation is obtained for currents less than 1.5ITh (Pout=30 mW/facet) and linear power output for measurements up to 2ITh. We attribute the favorable characteristics to the curvature of the grown layers which leads to the stabilization of the lateral modes.