Continuous-wave Highly Efficient Low-Divergence Terahertz Wire Lasers

S Biasco,L Li,D.A Ritchie,K Garrasi,H E Beere,A.G Davies,F Castellano,E H Linfield,M S Vitiello

doi:10.1109/irmmw-thz.2018.8510384

S Biasco, L Li + Show 7 more

Open Access

https://doi.org/10.1109/irmmw-thz.2018.8510384

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Abstract

In recent years, Terahertz (THz) quantum cascade lasers (QCLs) have undergone a fast development, showing high power, ultra-broadband gain and quantum-limited linewidth. For many applications, THz QCLs need to operate in continuous-wave (CW), with a tight control of the emission spectrum and highly collimated beam profiles. These requirements are usually addressed by exploiting distributed feedback (DFB), photonic crystals or micro-cavity architectures, which can allow tailoring either the laser beam divergence or the emission frequency, and eventually both of them simultaneously, as in the case of third-order DFBs. Here we report on an original design in which a wire DFB THz QCL, engineered with a lateral sinusoidal corrugation providing feedback and frequency control, and an array of surface hole provides light outcoupling. This new photonic structure has led to the achievement of low-divergence beams (10°), single-mode emission, high slope efficiencies (250 mW/A), and stable CW operation.

Highlights

Terahertz (THz) quantum cascade lasers (QCLs) have undergone rapid development since their demonstration, showing high power, broad-tunability, quantum-limited linewidth, and ultra-broadband gain
Microcavities[4], photonic crystals[5,6], and both pseudo-random[7,8] and random[9] photonic structures, can manipulate and confine light in small volumes, and at targeted frequencies. This has further expanded the functionality of the THz QCL, allowing operation at a single emission frequency[7] or over a broad (0.5 THz) frequency bandwidth, or with designed directional beam patterns[8]
We demonstrate double-metal waveguided distributed feedback (DFB) THz quantum cascade wire lasers, exploiting an innovative approach in which feedback is provided by a lateral sinusoidal ridge corrugation, while light extraction is separately controlled by a hole array in the top metallization

Summary

Introduction

Terahertz (THz) quantum cascade lasers (QCLs) have undergone rapid development since their demonstration, showing high power, broad-tunability, quantum-limited linewidth, and ultra-broadband gain. We demonstrate double-metal waveguided DFB THz quantum cascade wire lasers, exploiting an innovative approach in which feedback is provided by a lateral sinusoidal ridge corrugation, while light extraction is separately controlled by a hole array in the top metallization.

Results

Conclusion