A new distributed-feedback technique is developed to dramatically improve the laser beam patterns and increase the output power levels of THz quantum cascade lasers (QCLs). The invention enables a new kind of THz semiconductor laser with enhanced performance and suitability for mass-production.
Primary Application Area: Electronics, Sensors, Communications
Technology Development Status: Proven Manufacturability
DETAILED TECHNOLOGY SUMMARY
Narrow beam emission is highly required for most applications of metal-cavity semiconductor lasers and is difficult to realize when a laser cavity is of subwavelength dimensions. This is true for many types of nanocavity, microcavity lasers, and limits their practicability. A novel method, that we term as "antenna-feedback", of implementing distributed-feedback in the cavities of metal-cavity semiconductor lasers is developed both theoretically and experimentally for the first time. This concept of distributed-feedback in a semiconductor laser's cavity is completely new and significantly different from all other types of distributed-feedback techniques demonstrated for semiconductor lasers in past twenty-thirty years. Our technique provides distributed-feedback in semiconductor lasers that simultaneously makes a laser's cavity act like a phased-array antenna, which then leads to optical emission in a narrow beam. Distributed feedback is generally implemented with a variety of techniques for semiconductor lasers, primarily to obtain optical emission at a single frequency (or emission in single spectral-mode). Our unique technique achieves an ultra-narrow beam emission and high output power from the laser, which is otherwise very difficult to obtain from metal-cavity lasers due to the sub-wavelength dimensions of the emitting aperture.
FIGURES OF MERIT
Value Proposition: The scientific principle of this innovation is that by ensuring the predesigned phase condition, the mode traveling inside the laser waveguide is coupled/phase-locked to the mode traveling outside on the top metal, hence establishing a standing-wave on top of the structure in addition to one existing inside the laser cavity. Due to the subwavelength vertical dimension in the cavity, a large amount of electric field couples to a surface-plasmon mode attached to the top metal cladding, where the electrical field is exponentially decaying in air. There are specially designed apertures in the metal-cladding, which act like individual components of a phased-array antenna transmitter, resulting to low divergence laser beam in two dimensions.
We experimentally demonstrated the narrowest and best beam pattern quality for Terahertz (THz) Quantum cascade lasers (QCLs) to-date.
Organization Type: Academic/Gov Lab