Tapered Bragg reflection waveguide edge emitting lasers with near circular twin-beam emission

An edge emitting laser with two symmetrical near-circular spots located far field (FF) is demonstrated using tapered double-sided Bragg reflection waveguides (BRWs). The BRWs consist of six pairs of top p-type and bottom n-type Al-0.1 Ga-0.9 As/Al-0.3 Ga-0.7 As Bragg reflectors with a period thickness of 850 nm. The device has a 4 degrees tapered angle configuration and exhibits two stable circular beams with a separation angle of 52 degrees. Typical FF angles of 5.87 degrees and 7.8 degrees in the lateral and vertical directions, respectively, are achieved. The lateral FF angle in the ridged section is independent of the injection current (> 0.8 A) because of narrow ridge (similar to 10 mu m) confinement. By contrast, the FF angle in the tapered section shows an increase rate of 1.2-1.66 degrees/A. The periodic modulation of the lasing wavelength is observed to be sensitive to self-heating effects.