Very low threshold 1.55 μm grating coupled surface‐emitting lasers for optical signal processing and interconnect

We report in this work a record low threshold (∼4 mA, cw), 1.55 μm wavelength, grating‐coupled surface‐emitting laser (GCSEL) which rivals all other existing SELs in the 1.3 or/and 1.55 μm regions. Methods to improve the asymmetric far‐field patterns and to obtain even lower threshold SELs are also demonstrated and/or suggested.