Approaches to tuning the exceptional point of PT-symmetric double ridge stripe lasers

Abstract

Electrically injected Parity-time (PT)-symmetric double ridge stripe semiconductor lasers lasing at 980 nm range are designed and measured. The spontaneous PT-symmetric breaking point or exceptional point (EP) of the laser is tuned below or above the lasing threshold by means of varying the coupling constant or the mirror loss. The linewidth of the optical spectrum of the PT-symmetric laser is narrowed, compared with that of traditional single ridge (SR) laser and double ridge (DR) laser. Furthermore, the far field pattern of the PT-symmetric laser with EP below the lasing threshold is compared with that of the PT-symmetric laser with EP above the lasing threshold experimentally. It is found that when the laser start to lase, the former is single-lobed while the latter is double-lobed. when the current continues to increase, the former develops into double lobe directly while the latter first develops into single lobe and then double lobe again.

Transverse Photonic Crystal Mode Engineering for Broad-Area Semiconductor Lasers With Narrow-Divergence Angles

“…Proper optical feedback along the longitudinal direction of the cavity can also reduce the number of the high-order modes, and enhance the oscillation of the fundamental mode [9], [10], [11]. Besides, lateral coupling structures can be adopted to couple the high-order modes, and decrease their optical confinement factor in the region injected with currents, filtering out the high-order modes as well [12], [13], [14], [15], [16], [17], [18], [19]. Among those lateral coupling strategies, supersymmetry, originating from quantum systems [20], [21], [22], [23], [24], [25], [26], can construct superpartners, possessing part of optical eigenvalues of the origin BA laser, to selectively couple the high-order modes of the BA laser [19].…”

Transverse photonic crystal semiconductor laser arrays

“…According to combining the Γ-factor engineering with chirped ridge waveguides [8], the ridge-waveguide laser array can emit with a single-lobe horizontal far-field pattern at higher injection currents. In addition to the traditional mode control methods, some physical concepts originating from quantum systems are also introduced to design the semiconductor laser arrays, such as paritytime symmetry [9,10], supersymmetry [11][12][13] and so on. Among them, supersymmetric transformations can construct the superpartners of the original laser array, which can couple the high-order supermodes of the original laser array while limiting the extension of the fundamental supermode based on the global phase matching conditions [14].…”