High-power Al-free active region (lambda = 852 nm) laser diodes for atomic clocks and interferometry applications

Abstract

We have developed Fabry-Perot lasers at &#955;=852nm, using an aluminium free active region with the aim to develop a single-frequency and single spatial mode device for atomic clocks and interferometry applications. The device is a separate confinement heterostructure with a GaInP large optical cavity and a 8nm compressive-strained GaInAsP quantum well. The broad-area (100&#956;m wide) laser diodes are characterised by low internal losses (<3 cm^-1), a high internal efficiency (94%) and a low transparency current density (100A/cm²) which illustrates the quality of the laser structure. For an AR/HR coated 2mm long broad area laser diodes we measure a low threshold current density (245A/cm²) and a high slope efficiency (0.9 W/A). We obtain an optical power of more than 5.5W (I= 8.5A), under CW operation at 15°C, with a maximum wall-plug efficiency of 0.45. The lasing emission is achieved up to at least 115°C An optical power of more than 1.4W is obtained at 100°C (I=3.6A). A power of 1.2W (I=1.7A, 15°C) is achieved at 852nm. For an AR/HR coated 2mm long 4&#956;m wide ridge waveguide laser diode, we obtain a low threshold current (46mA) and a high slope efficiency (0.9W/A). We obtain 852nm wavelength at 145mW (I=200mA, 15°C). We measure an optical power of 180mW (I=240mA) in a single spatial mode with the beam quality parameter M²=1.5. At 180mW both near and far field are gaussian-shaped with respective full widths at 1/e² of 6&#956;m and 12°.