Continuous-wave operation of (Al,In)GaN distributed-feedback laser diodes with high-order notched gratings

Abstract

We report on the continuous wave, room temperature operation of a distributed-feedback laser diode (DFB-LD) with high-order notched gratings. The design, fabrication and characterization of DFB devices, based on the (Al,In)GaN material system, is described. The uncoated devices were mounted into TO packages for characterization and exhibited single wavelength emission at 408.6 nm with an optical power of 20 mW at 225 mA. A side mode suppression ratio (SMSR) of 35 dB was achieved, with a resolution limited full-width at half maximum of 6.5 pm.

GaN-based distributed feedback laser diodes for optical communications

“…To enable a single-wavelength GaN laser to operate, a sidewall grating was etched into (Al,In,Ga)N based laser epitaxial structures, with fabrication details outlined in [9] [10]. For a first-order grating to be realised, feature sizes would be ~40 nm, which is currently impossible due to the technological limitations present in current etching tools.…”

“…To maximise the coupling coefficient, as 3 rd order gratings exhibit weaker coupling coefficients compared to their 1 st -order counterparts, an 80% duty cycle was implemented for the application of a third order grating [11]. In this work, however, devices based on 39 th order notched gratings were used [12], which provide somewhat easier etching methods compared to a previously discussed 3 rd -order grating device [7] [10]. The main advantage of the higher-order grating geometry is the potential for a much narrower linewidth.…”

10-Gbit/s Sky-Blue Distributed Feedback Laser Diode-Based Visible Light Communication

“…While DFB-LDs are now widely available at the telecom wavelengths, they are relatively unexplored at the visible wavelengths. Device development has shown InGaN-based DFB-LDs emitting at violet, blue, and green wavelengths [6][7][8][9][10], but aside from a recent report [11], their application to optical wireless communications is little-known.…”

Recent progress in distributed feedback InGaN/GaN laser diodes

“…Buried gratings require complex overgrowth steps which have the potential to introduce growth defects while surface grating designs can compromise the quality of the p-type top contact. In our DFB laser implementation, gratings are formed along the sidewalls of a ridge waveguide laser diode [6][7] [8]. It's one of the simplest ways (in terms of complexity of fabrication) to achieve single wavelength operation and has the advantage that the sidewall grating can be designed and implemented entirely post growth once the emission wavelength is known.…”