Photonic crystal nanobeam lasers

Abstract

Photonic crystal lasers operating at room temperature based on high Q/V nanobeam cavities have been demonstrated. We reported a large spontaneous emission factor (β~0.97) by fitting the L-L curve with the rate equations.Photonic crystal lasers, 1 with small mode volumes (V) and high Quality (Q) factors, have enhanced photon emission below threshold via Purcell effect, [2][3][4] and can operate with high modulation speeds. 5, 6 Moreover, threshold-less lasing has been predicted in photonic crystal cavities, with necessary but not sufficient condition that the spontaneous emission factor (β) amounts to unity. 7, 8 Most photonic crystal lasers so far have been demonstrated based on two-dimensional (2D) photonic crystal slabs. Recently nanobeam structures attracted extensive interests because of their capability to achieve ultra-high Q/V factors in much smaller footprint. [9][10][11] We emphasize a small mode volume of these resonators, close to the diffraction limit [(λ/2n) 3 ], that is crucial for realization of large Purcell factor in solid-state emitters with a considerable homogeneous broadening (e.g. bulk semiconductors, semiconductor quantum wells at room temperature). In addition, nanobeam cavities do not have mode degeneracy, 12-15 and therefore can support a single cavity mode over a broad spectrum. This single-mode nature is important for a large β factor and reduction of lasing threshold 8 . In this work we report the experimental demonstration of photonic crystal nanobeam lasers operating at room temperature.The nanobeam cavities are designed using the same approach as our previous work. 9 The cavity is designed, using three dimensional finite-difference time-domain (3D-FDTD) modeling, to support a fundamental TE-like mode at 1.59µm, polarized predominantly along x-axis. Field components of the fundamental mode are shown in Fig. 1(a). The electric field density is concentrated in the dielectric region, leading to a large confinement factor needed for a lasing action. The mode volume of this mode is 0.28(λ/n) 3 , which is close to the diffraction limit, and its passive Q factor is larger than 8,000,000. In addition, the cavity supports another mode at a longer wavelength (1.72µm). This is an extended mode, with a node in the center of the structure and a larger mode volume of 0.67(λ/n) 3 . Our cavities are fabricated in a 330nm thick, MOCVD grown, In 0.53 (Al 0.4 Ga 0.6 ) 0.47 As slab that contains four compressively strained In 0.58 Ga 0.42 As quantum wells placed at the center of the slab. Active layer's emission is maximized at wavelength of 1.59µm, and is transverse-electric (TE) polarized due to the strain. The slab is grown on top of a 1µm thick sacrificial InP layer. Top-down fabrication sequence, based on e-beam lithography (using negative Foxx resist) followed by ICP reactive ion etching (BCl 3 /HBr chemistry) is used to realize the structures. The remaining mask layer is then removed in HF, and nanobeams are released in 3:1 HCl:H 2 O solution at 11ºC. The final fabricated structu...

Design of a Novel Micro-Laser Formed by Monolithic Integration of a III-V Pillar With a Silicon Photonic Crystal Cavity

“…The coupling to nonlasing modes can be greatly suppressed in a nanocavity that has a very large free spectral range, while the coupling to leaky modes has been calculated to be close to unit [26] for a structure that is very similar to the one discussed in this paper. For simplicity, is used in the following calculations.…”

“…The strong coupling between optical modes and gain medium can change the spontaneous emission rate dramatically. This so-called Purcell effect [19] can be quantified through the Purcell factor , whose expression is given by [24]- [26]: (1) where , and are the effective mode volume, and central wavelength of the cavity mode. n is the refractive index at the field maximum.…”

“…In addition, the associated Purcell effect [19] could further reduce the threshold current [20] and increase the modulation bandwidth [21], [22]. Threshold-less lasing has been demonstrated in devices where the spontaneous emission factor was increased to unity [23]- [26]. In this work we will focus on one-dimensional (1-D) PhC cavities, which, compared to the more extensively explored two-dimensional PhC cavities, can achieve a sufficiently high Q/V factor within a much smaller overall footprint.…”

Electrically Driven Photonic Crystal Nanocavity Devices

“…[45], [46]. They have also been used to demonstrate low threshold lasers, optomechanical crystals, and chemical sensors [47]- [49]. We show that in spite of their narrow cross sections, nanobeam cavities can be efficiently electrically pumped by a lateral p-i-n junction [35].…”

High-Q/V air-mode photonic crystal cavities at microwave frequencies

“…1(a) [13][14][15][16][17]. We choose a refractive index of 3.1 for the rod, which corresponds to the refractive index of alumina (Al 2 O 3 ) at microwave frequencies.…”