Engineering Multi-Section Quantum Cascade Lasers for Broadband Tuning

Steven Slivken,Manijeh Razeghi

doi:10.3390/photonics3030041

Steven Slivken, Manijeh Razeghi

Open Access

https://doi.org/10.3390/photonics3030041

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Abstract

In an effort to overcome current limitations to electrical tuning of quantum cascade lasers, a strategy is proposed which combines heterogeneous quantum cascade laser gain engineering with sampled grating architectures. This approach seeks to not only widen the accessible spectral range for an individual emitter, but also compensate for functional non-uniformity of reflectivity and gain lineshapes. A trial laser with a dual wavelength core is presented which exhibits electroluminescence over a 750 cm−1 range and discrete single mode laser emission over a 700 cm−1 range. Electrical tuning over 180 cm−1 is demonstrated with a simple sampled grating design. A path forward to even wider tuning is also described using more sophisticated gain and grating design principles.

Highlights

One of the primary appeals of the quantum cascade laser (QCL) is its ability to access a wide portion of the infrared spectrum (3 < λ < 11 μm) in continuous operation at room temperature [1,2]
High output power and a small form factor are key characteristics. This makes the QCL a very important, even enabling, technology for many applications which would benefit from portability, such as spectroscopy
While initial development concentrated on fixed frequency applications, recent years have seen a resurgence in QCL development based on wide wavelength coverage from a single device

Summary

Introduction

One of the primary appeals of the quantum cascade laser (QCL) is its ability to access a wide portion of the infrared spectrum (3 < λ < 11 μm) in continuous operation at room temperature [1,2]. With a QCL, a single, homogeneously broadened emitter can exhibit several hundred inverse centimeters of bandwidth, especially at shorter wavelengths This is one advantage of an intersubband emitter over a mid-infrared interband laser like the interband cascade laser (ICL). Though there are many geometries that can exhibit the Vernier effect, one of the most successful for the QCL at present is the sampled grating distributed feedback (SGDFB) laser This architecture is similar to that developed for electrical tuning of telecom lasers [7], and was demonstrated for the QCL in 2012 [8]. Combining the SGDFB with an additional distributed Bragg reflector section has been used to generate a tunable dual wavelength laser This was utilized recently as an on-chip pump source for room temperature, single mode, tunable continuous wave THz emission [13]

Combining Broadband Gain and Electrical Tuning

design is typically

Discussion

Conclusions