Single spatial mode 3 µm diode lasers with continuous-wave output power of 15 mW at room temperature

Abstract

Single spatial mode GaSb-based type-I quantum well diode lasers with 3 mm emission and continuous-wave output power above 15 mW at room temperature are reported. The devices with 5.5 mm-wide ridge waveguides were fabricated by selective wet etching technique.Introduction: Diode lasers with a type-I quantum well (QW) active region and grown on GaSb substrates operate in continuous-wave (CW) regime at room temperature up to 3.44 mm [1]. GaSb-based narrow ridge waveguide lasers with diffraction limited output operating within the spectral region near 3 mm with output of several mWs have been fabricated by different groups [2 -4]. The ridge waveguides of these devices were fabricated using the reactive ion etching (RIE) technology. In this Letter, we report on the development of 3 mm GaSbbased diode lasers with narrow ridge waveguides fabricated by wet etching technique. The wet etching technique can be realised cost-effectively and often has minimal (if any at all) negative effect on protected non-etched sections.The single spatial mode diode lasers generated record output power of 16 mW at 208C. The slow axis beam divergence in the far field was about 308 full-width-at-half-maximum (FWHM) for 5.5 mm-wide ridge waveguide lasers. Studies of the effect of the ridge width on laser efficiency, modal gain and loss revealed that the threshold current density of the narrow ridge lasers (5.5 mm wide) increases due to the extra 8 cm 21 of the internal loss and as a result of the rise of the role of the lateral current spreading effect.

Room temperature operated diffraction limited λ ≃ 3 µm diode lasers with 37 mW of continuous‐wave output power

“…Total optical loss for the both devices was about 26 cm −1 . Previously reported 5.5 µm-wide deep wet etched lasers demonstrated about 8 cm −1 of internal loss increase as compared to reference 100 µm-wide devices [5]. Thus the efficiency of the well-controlled shallow ridge formation by chlorine-free ICP RIE was confirmed.…”

“…The devices demonstrated the record output power of 37 mW at 17°C. This is more than a twofold improvement as compared to the previous record of about 15 mW CW obtained for wet etched lasers [5]. The dry etched devices maintained the single spatial mode operation with ∼10° FWHM far‐field pattern (inset of Fig.…”

“…The wafer was processed into dielectric confined ridge waveguide lasers with the ridge widths of 5.5 and 100 µm. It should be noted that wide ridge multimode lasers used in [5] and used in this work both demonstrated similar efficiencies and output power levels above 300 mW CW at room temperature.…”

“…Chlorine-based dry etching technology enabled precise control of etching profile but required extensive operational costs. Our research group has previously developed the two-step selective wet etching technique that was used to fabricate GaSb-based diffraction limited lasers [4,5]. The devices emitting near 3 µm had ∼5.5 µm-wide ridges etched down to the interface between the pcladding and the waveguide core that served as an etch stopper.…”

“…Device design and fabrication: The laser heterostructure used in this work was emitting near 3 µm. The design of the laser heterostructure was similar to the one reported in [5]. The wafer was processed into dielectric confined ridge waveguide lasers with the ridge widths of 5.5 and 100 µm.…”