Terahertz master-oscillator power-amplifier quantum cascade lasers

Abstract

We report on the realization of a monolithically integrated master-oscillator power-amplifier architecture in a terahertz quantum cascade laser (THz-QCL) with a metal-metal waveguide. The master-oscillator section is a first-order distributed feedback (DFB) laser. Instead of using a thick anti-reflection coating, we exploit a diffraction grating together with an absorbing boundary in the power-amplifier section to efficiently extract the laser radiation and suppress the self-lasing in it. The devices demonstrate a stable generation and power amplification of single-mode emission. The amplification factor is about 5, and the output power is approximately twice that of the standard second-order DFB lasers fabricated from the same material. Emission beam pattern with a divergence angle of $18 Â 40 is achieved. Our work provides an avenue for the realization of singlemode THz-QCLs with high output power and good beam quality. Published by AIP Publishing.[http://dx.doi.org/10.1063/1.4969067] Terahertz quantum cascade lasers (THz-QCLs) with single-mode emission are highly desired for applications such as spectroscopy, trace gas detection, and free space communication.1-3 Intensive studies have been devoted to develop unique photonic coupling structures in order to approach a high output power and a directional beam pattern for singlemode THz-QCLs. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] Related results include third-order distributed feedback (DFB) lasers, 5,6 second-order DFB THzQCLs with dual slits, 7 THz-QCLs with a graded photonic heterostructure resonator, 9-11 phase-locked arrays of secondorder DFB lasers, 12-14 etc. However, to ensure that lasing occurs on transverse and longitudinal single-mode, the dimensions of the photonic coupling structure must be limited, thus restricting the available output power and increasing the divergence of the emitted beam.Monolithically integrated master-oscillator power-amplifier (MOPA) is a promising architecture to realize single-mode emission with a high output power and a near diffractionlimited beam quality. It has been implemented in near-infrared diode lasers and also in mid-infrared quantum cascade lasers. [18][19][20][21][22] In order to suppress the self-lasing in the poweramplifier (PA) section and to fully exploit the material gain, the front facet of the PA section needs to be coated by antireflection (AR) layers. However, extending the MOPA architecture to the THz frequency range is a challenge because of the lack of suitable AR coatings.Only a few researches related to MOPA devices based on THz quantum cascade structures have been reported. 23,24 In these devices-which are based on a single plasmon waveguide-the master oscillator (MO) section is a Fabry-P erot laser and is separated from the PA section by a deep air gap. The PA section is another Fabry-P erot cavity with one facet angled or coated by a thick parylene layer. The Fabry-P erot MO section intrinsically results in multimode emission, while the deep air gap degrades the coupling efficiency o...

High performance terahertz quantum cascade lasers

“…SISP edge-emitting and MM surface-emitting. The MM surface-emitting THz QCL is often realized by incorporating high-order DFB grating [9][10][11][12][13], which is advantageous for the directional beam pattern and high beam quality. However, the output power is limited severely by the grating coupling mechanism that the radiation perpendicular to the plane is provided by the first-order diffraction of the high-order DFB grating while the feedback parallel to the plane is offered by the second-order diffraction.…”

Modeling and improving the output power of terahertz master-oscillator power-amplifier quantum cascade lasers

“…Among these novel laser cavities, master-oscillator power-amplifier (MOPA) is a promising configuration to realize high performance in terms of output power, wall-plug efficiency and beam quality. We recently demonstrated the first master-oscillator power-amplifier quantum cascade laser in the terahertz frequency range (THz-MOPA-QCL) [32,33]. In such a MOPA device, the master-oscillator (MO) section is a first-order DFB laser, while the power-amplifier (PA) section consists of a preamplifier and a grating coupler.…”

Гетероструктуры Одночастотных И Двухчастотных Квантово-Каскадных Лазеров

“…Рекордная выходная оптическая мощность излучения ККЛ на РЧ, сформированных на подложках InP и измеренная при 293 K, составляет 76 мкВт ( f = 3.4 ТГц) [7,8]. Применение технологии спекания пластин, ранее апробированной для тера-герцовых ККЛ, выращенных на подложках GaAs [9][10][11], а также вертикально-излучающих лазеров [12][13][14][15] позволило уменьшить поглощение выводимого те-рагерцового излучения в материале подложки (вы-вод излучения через кремний вместо InP) и уве-личить выходную оптическую мощность до 270 мкВт ( f = 3.5 ТГц) [16].…”