Phase-locked array of quantum cascade lasers with an integrated Talbot cavity

Abstract

Abstract:We show a phase-locked array of three quantum cascade lasers with an integrated Talbot cavity at one side of the laser array. The coupling scheme is called diffraction coupling. By controlling the length of Talbot to be a quarter of Talbot distance (Z t /4), in-phase mode operation can be selected. The in-phase operation shows great modal stability under different injection currents, from the threshold current to the full power current. The far-field radiation pattern of the in-phase operation contains three lobes, one central maximum lobe and two side lobes. The interval between adjacent lobes is about 10.5°. The output power is about 1.5 times that of a single-ridge laser. Further studies should be taken to achieve better beam performance and reduce optical losses brought by the integrated Talbot cavity. References and links

Tapered Quantum Cascade Laser Arrays Integrated with Talbot Cavities

“…1 , our Talbot cavity length was determined to be Z t /8 similar to ref. [ 19 ] which is around 104 μm in this letter. Figure 2 shows the sketch and microscope pictures of the device.…”

“…These structures either bring about large losses in the waveguide [ 15 ] or result in heat accumulation by pursuing a short adjacent distance to obtain the coupling [ 16 – 18 ]. Recently, diffraction-coupled QCL arrays that integrated a side cavity based on diffraction-coupled Talbot effects were reported [ 19 ]. In the diffraction-coupled structure, the coupling occurs in the Talbot cavity by the diffraction of the ridge end and reflection of the cavity facet.…”

Talbot coupling of an array of quantum cascade lasers

“…6 In the past, Talbot arrays have been investigated using single transverse mode diode laser arrays but not QCLs except in two very recent papers in which phase-locking using broad area emitters is unveiled. 7,8 In this paper, we investigate both theoretically and experimentally the complex dynamics arising in an array of QCLs. 9 We provide a comprehensive analysis of the Talbot cavity and show the existence of distinct regions depending on whether all the lasers are locked to the same frequency.…”

Spectrally resolved modal characteristics of leaky-wave-coupled quantum cascade phase-locked laser arrays

“…As described below, resonant leaky-wave coupling has also been employed for obtaining global coupling in THz phase-locked QCL arrays. 5,6 Global coupling has also been achieved using antenna mutual coupling for phase locking two-dimensional (2-D) surface-emitting arrays of THz DFB QCLs, up to 6.5 mW peak power at 10 K. 7 Integrated Talbot cavities have been used at the back end of phase-locked three-element 8 and six-element 9 ridge-guide laser arrays for intermodal discrimination. For the threeelement array, 8 up to 375 mW were obtained in an in-phase, near-DL beam pattern, but at a serious penalty in efficiency (e.g., halving of the slope efficiency) most likely due to strong edge diffraction losses in the Talbot cavity of such low-element-number arrays.…”

“…5,6 Global coupling has also been achieved using antenna mutual coupling for phase locking two-dimensional (2-D) surface-emitting arrays of THz DFB QCLs, up to 6.5 mW peak power at 10 K. 7 Integrated Talbot cavities have been used at the back end of phase-locked three-element 8 and six-element 9 ridge-guide laser arrays for intermodal discrimination. For the threeelement array, 8 up to 375 mW were obtained in an in-phase, near-DL beam pattern, but at a serious penalty in efficiency (e.g., halving of the slope efficiency) most likely due to strong edge diffraction losses in the Talbot cavity of such low-element-number arrays. For the six-element array, 9 4 W near-DL peak power was obtained in both the in-phase and out-of-phase array modes, as expected from theory 10 when the Talbot-cavity length is equal to one-half of the Talbot distance Z t .…”