We report on deeply etched sidewall grating DFB lasers in the InGaN/GaN material system emitting at a single wavelength around 434 nm. GaN lasers have a wide range of applications in communications, displays and storage. The availability of a single wavelength device with a good side mode suppression ratio (SMSR) would allow further applications to be addressed such as sources for laser cooling and Fraunhofer line operation for solar background free communications. Sidewall etched gratings have the advantage of fabrication with no need for overgrowth and have been demonstrated in a range of other material systems and wavelengths. Importantly for GaN based devices, this design has the potential to minimise fabrication induced damage to the epi structure. We investigated two laser designs, one with 80 % duty-cycle 3rd order gratings and another with 39th order partial gratings. Simulation of the 2D waveguide sections was carried out to find the optimal grating width. For fabrication, the laser ridge and gratings were patterned in a single step using electron beam lithography and ICP etched to a depth of 500 nm. Contact metal was deposited and the sample thinned and cleaved into 1 mm long cavities. The as-cleaved 3rd order lasers emit in the pulsed regime with a SMSR of 20 dB and a peak single-mode output power of 40 mW. The output power is similar to that of parallel processed FP lasers. The 39th order lasers also exhibit narrow spectral width at an output power of 10 mW.
[1]
Guo-Qiang Lo,et al.
Hybrid III-V/silicon laser with laterally coupled Bragg grating.
,
2015,
Optics express.
[2]
Takashi Mukai,et al.
CW Operation of the First-Order AlInGaN 405 nm Distributed Feedback Laser Diodes
,
2006
.
[3]
Guofeng Song,et al.
Two-dimensional simulation of high-order laterally-coupled GaAs-AlGaAs DFB laser diodes
,
2004
.
[4]
B. Corbett,et al.
Analysis of Slot Characteristics in Slotted Single-Mode Semiconductor Lasers Using the 2-D Scattering Matrix Method
,
2006,
IEEE Photonics Technology Letters.
[5]
Q. Lu,et al.
Design of Slotted Single-Mode Lasers Suitable for Photonic Integration
,
2010,
IEEE Photonics Technology Letters.
[6]
S Y Zhang,et al.
$\lambda \sim {3.35}\ \mu$m Distributed-Feedback Quantum-Cascade Lasers With High-Aspect-Ratio Lateral Grating
,
2011,
IEEE Photonics Technology Letters.
[7]
Piotr Perlin,et al.
A multi-wavelength (u.v. to visible) laser system for early detection of oral cancer
,
2015,
Photonics West - Biomedical Optics.