All-optical adaptive control of quantum cascade random lasers

Abstract

Spectral fingerprints of molecules are mostly accessible in the terahertz (THz) and mid-infrared ranges, such that efficient molecular-detection technologies rely on broadband coherent light sources at such frequencies. If THz Quantum Cascade Lasers can achieve octave-spanning bandwidth, their tunability and wavelength selectivity are often constrained by the geometry of their cavity. Here we introduce an adaptive control scheme for the generation of THz light in Quantum Cascade Random Lasers, whose emission spectra are reshaped by applying an optical field that restructures the permittivity of the active medium. Using a spatial light modulator combined with an optimization procedure, a beam in the near infrared (NIR) is spatially patterned to transform an initially multi-mode THz random laser into a tunable single-mode source. Moreover, we show that local NIR illumination can be used to spatially sense complex near-field interactions amongst modes. Our approach provides access to new degrees of freedom that can be harnessed to create broadly-tunable sources with interesting potential for applications like self-referenced spectroscopy.

Ultrafast Generation of Coherent Phonons in Two-Dimensional Bismuthene

“…Generally, a low-frequency acoustic phonon has the characteristics of directional propagation, information modulation, and less information distortion, intrinsically beneficial for information transmission, but the acoustic phonon transmission of three-dimensional (3D) materials is omni-directional; that is, it is difficult to achieve controllable information transmission. Alternatively, 2D materials can only be transmitted in the plane .…”

Self‐Induced Mode‐Locking in Electrically Pumped Far‐Infrared Random Lasers

“…A variety of approaches has been adopted to control RL modes [22] , such as tuning of the scatterer statistic arrangement and concentration, [23] external cavity configurations, [8] or the reshaping of their spectral emission via adaptive optical pumping. [24] Spontaneous mode-locking in RLs was theoretically predicted. [18,25] The complex tunable optical pumping of a laser dye [25] was exploited to promote the transition of RL modes from a resonant feedback regime, characterized by few uncorrelated sharp peaks, to an incoherent one, compatible with the emission of a smooth broader spectrum with a high degree of correlation.…”

“…Disordered RLs, originally conceived in optically pumped suspended microparticle laser dye, [27] fine powders, [28] or bone tissues, [29] were reported in the technologically appealing mid-IR (9-10.5 μm) [30] and terahertz (THz) (2.8-3.5 THz) [23,8,[31][32][33] frequency ranges, exploiting electrically pumped QCLs embedded in either one dimensional, 1d [31] , or two dimensional, 2d [23] , photonic resonators. Through a combination of different designs [23] and architectures, [8,[24][25][26][27] large power outputs (80 mW peak power) and rich (up to 13 modes) multimode emission, over the entire optical bandwidth of the designed QC structure (450 GHz) in both pulsed and continuous-wave (CW) [14,32] were achieved. Broadband spectroscopic and multicolor speckle-free imaging applications can benefit from the development of mode-locked RLs across the THz.…”

“…A variety of approaches has been adopted to control RL modes [ 22 ] , such as tuning of the scatterer statistic arrangement and concentration, [ 23 ] external cavity configurations, [ 8 ] or the reshaping of their spectral emission via adaptive optical pumping. [ 24 ]…”

Single‐Shot Interaction and Synchronization of Random Microcavity Lasers

“…With the progress of the above researches, coupling and synchronization of individual lasers in disordered structure has become an emerging topic, since it plays a pivotal functional role in the collective behavior of complex systems as well as providing a large degree of randomness and freedom, and would be the basis of a variety of network architectures such as learning machines of computing circuit and node structures of neuronal circuit. [ 22–24 ] Numerous random cavities’ structures have been studied such as multi‐quantum‐well with air‐holes, [ 25 ] biological tissues, [ 26 ] wrinkled 2D materials, [ 27 ] and networks of cellulose nanofibers, [ 28 ] which mainly focus on the collective output characteristics. Generally, lasing is carried by connected links between each pair of scatterers, inspiring people to pursue an all‐optical network combination in disordered systems.…”