Prospects and merits of metal-clad semiconductor lasers from nearly UV to far IR.

Jacob B Khurgin

doi:10.1364/oe.23.004186

Abstract

Using metal-clad (or plasmonic) waveguide structures in semiconductor lasers carries a promise of reduced size, threshold, and power consumption. This promise is put to a rigorous theoretical test, that takes into account increased waveguide loss, Auger recombination, and Purcell enhancement of spontaneous recombination. The conclusion is that purported benefits of metal waveguides are small to nonexistent for all the band-to-band and intersubband lasers operating from UV to Mid-IR range, with a prominent exception of far-IR and THz quantum cascade lasers. For these devices, however, metal waveguides already represent the state of the art, and the guiding mechanism in them has far more in common with a ubiquitous transmission line than with plasmonics.

Highlights

In the last half century semiconductor lasers (SL) have come a long way from being laboratory curiosity to becoming indispensable in every walk of life [1]
The salient features of SL’s – compact size, high efficiency and ability to be modulated at high speed assure that the range of SL applications expands in step with the expansion of the range of wavelengths in which SL’s can operate
The validity of using the term “plasmonic” versus less trendy “metal clad” will be discussed further on, but one can summarize the practical developments by saying that metalclad lasers with sub-wavelength confinement in one or two dimensions had been successfully demonstrated in various spectral regions with varied results

Summary

Introduction

In the last half century semiconductor lasers (SL) have come a long way from being laboratory curiosity to becoming indispensable in every walk of life [1]. All of these techniques are bounded by the diffraction limit there has been an extensive effort to circumvent the diffraction limit by various techniques, typically involving use of metals [4] These efforts coincided with rapid advancements in the field of plasmonics [5], where the field concentration on the sub-wavelength scale have been achieved and successfully used to enhance various linear and nonlinear optical processes. For these reasons, any laser structure incorporating metal had become known as a “plasmonic”, or, better “nano-plasmonic laser” [6,7,8,9,10,11,12,13,14,15,16]. Our results will show that delicate interplay of many factors: loss in the metal, free carrier loss in semiconductor, Auger recombination, Purcell enhancement of radiative rate leads to dramatically different results in different spectral regions

Surface plasmon polaritons and metal-clad waveguides

Injection pumped metal clad SL’s in the visible to near IR ranges

Metal clad quantum cascade lasers

Findings

Conclusions