Designer Multimode Localized Random Lasing in Amorphous Lattices at Terahertz Frequencies

Abstract

Random lasers are a special class of laser in which light is confined through multiple scattering and interference process in a disordered medium, without a traditional optical cavity. They have been widely studied to investigate fundamental phenomena such as Anderson localization, and for applications such as speckle-free imaging, benefitting from multiple lasing modes. However, achieving controlled localized multi-mode random lasing at long wavelengths, such as in the terahertz (THz) frequency regime, remains a challenge.Here, we study devices consisting of randomly-distributed pillars fabricated from a quantum cascade gain medium, and show that such structures can achieve transversemagnetic polarized (TM) multi-mode random lasing, with strongly localized modes at THz frequencies. The weak short-range order induced by the pillar distribution is sufficient to ensure high quality-factor modes that have a large overlap with the active material.Furthermore, the emission spectrum can be easily tuned by tailoring the scatterer size and filling fraction. These "designer" random lasers, realized using standard photolithography 2 techniques, provide a promising platform for investigating disordered photonics with predesigned randomness in the THz frequency range, and may have potential applications such as speckle-free imaging.

Photonic Engineering Technology for the Development of Terahertz Quantum Cascade Lasers

“…Conversely, the light takes a random walk in the random photonic structures as the reciprocal Fourier spectrum has a uniform and isotropic pattern without obvious dominant peaks. [52,[159][160][161][162][163] Comparing with other random laser systems, for example, nanocrystalline ZnO powers, [164] ceramics, [165] organic composites, [166] nanoparticles dispersed in fluorescent dyes, [167] and semiconductor membranes, [168] random laser based THz QCL is advantageous for its electrical pumping scheme and compact fingerprint. [157] Thanks to the special characteristics, random photonic structures of various configurations have been implemented as laser cavities for the study of the fundamental physics (e.g., the feedback mechanism, light-matter interaction, modal localization) as well as practical applications (e.g., speckle-free imaging, display lighting, medical diagnostic, and sensing).…”

“…Even so, the wave interference still maintains, leading to typical random modes with gigantic field intensity fluctuations and even subwavelength localization profiles, [156] analogous to the Anderson localization of electrons in the disordered semiconductors. [160,161] As a result, such a random laser could achieve multiple strongly localized mode lasing with subwavelength modal volumes as shown in Figure 13f, allowing for device miniaturization. [158] The random lasing based on THz QCLs has been achieved recently.…”

“…[157] Thanks to the special characteristics, random photonic structures of various configurations have been implemented as laser cavities for the study of the fundamental physics (e.g., the feedback mechanism, light-matter interaction, modal localization) as well as practical applications (e.g., speckle-free imaging, display lighting, medical diagnostic, and sensing). Despite the intrinsic randomness, modulation of scatterer densities, adoption of short-or longrange order, [52,160] and disk boundary [162,163] were implemented to tailor the THz random laser emission properties including the lasing threshold, operation wavelengths, and farfield patterns, indicating the possibility of taming the laser for specific functionalities. [52,[159][160][161][162][163] Comparing with other random laser systems, for example, nanocrystalline ZnO powers, [164] ceramics, [165] organic composites, [166] nanoparticles dispersed in fluorescent dyes, [167] and semiconductor membranes, [168] random laser based THz QCL is advantageous for its electrical pumping scheme and compact fingerprint.…”

“…The THz antennas, operating similarly to those in microwave devices, are on-chip integrated as generalists for beam, power, and polarization manipulation. [160] Copyright 2016, American Chemical Society. With more than ten years' efforts, the progress in the understanding of the THz QCL optical properties and the development of photonic design techniques have led to unprecedented achievements on single or plural aspects of THz QCL outputs.…”

The controllable intensity and polarization degree of random laser from sheared dye-doped polymer-dispersed liquid crystal

“…Random laser is a stimulated emission phenomenon observed in disordered media, such as nanoparticles [1,2], biomaterials [3], quantum cascade gain medium [4], semiconductors [5,6], and liquid crystals [7][8][9]. The feedback of random laser is realized by multiple scattering of light.…”