Physics and applications of IV-VI compound semiconductor lasers

Abstract

Lasers made of lead salt compounds have proven to be best suited for coverage of the mid-infrared region from 3 to 30 pm. Nowadays doubleheterostructure (DH) lasers are the standard, using as active layers PbEuSSe for the short-wavelength region below 4 pm, PbEuTeSe or PbEuSe for the 4-8 pm range and PbSnTe or PbSnSe for wavelengths beyond 8 pm. Originally liquid phase epitaxy but now molecular beam and hot wall epitaxy techniques are most commonly used to produce a wide variety of laser structures. While Simple DH lasers with contact or mesa stripes for lateral confinement prevail in commercial devices, highly sophisticated prototypes with buried layer, corrugated distributed Bragg reflector (DBR) and distributed feedback (DFB) and single-and multi-quantumwell structures have been successfully manufactured. Gas spectroscopy has remained the main field of application where mode quality and tuning properties of the emitted radiation are most important. The dominant development goal has been the increase of the operating temperature to make the use of simple cooling equipment possible. Theoretical models for threshold current calculations have been established; however, the reliability of the results has been impaired by the fact that basic material properties of the ternary and quaternary compounds are not well known. In the course of this paper the state of the art and the development trends of lead salt lasers are described. The various fields of applications are summarised. Two examples-one dealing with car exhaust monitoring, the other with clinical isotopic ratio measurements of the exhaled breath-will be discussed in some detail

Thermal expansion of a lead sulfide nanofilm

“…Owing to a narrow band gap of 0.41eV and a high photosensitivity in the infrared range lead sulfide (PbS) found applications in optoelectronics, power engineering, and sensor based systems [1,2]. The optical and electronic properties of the PbS change when the crystallite sizes decrease below~20-40 nm [3][4][5].…”

Mid-Infrared Surface-Emitting Two Dimensional Photonic Crystal Semiconductor Lasers

“…Lead salt or IV-VI semiconductor system has been used as a major material source for mid-IR diode lasers for a long time, because of its energy bandgap covering the wavelength region from 3 to 30 m (Preier, 1990;Ishida & Fujiasyu, 2003;Tacke M. , 2000) and also its near two orders of magnitude lower non-radiative Auger recombination rates as compared to other conventional narrow band gap semiconductors (Findlay, et al, 1998). In this section, the realization of surface emitting photonic crystal lasers based on the lead salt compounds is described.…”

Physical vapor transport of lead telluride

“…wide wavelength operating range, high mobilities, good thermoelectric properties, tunability, narrow line width, and high local and temporal resolution [5]. Other advantages of these materials are: good homogeneity, rather low price, and easier manufacturing processes relative to HgTe-based materials.…”

“…Other advantages of these materials are: good homogeneity, rather low price, and easier manufacturing processes relative to HgTe-based materials. Bulk crystals of these materials are used mostly as substrates for manufacturing different devices, primarily tunable diode lasers operable in the midinfrared region from 3 to 30 microns and room temperature IR detectors operating in the range 2 -4.5 micrometer.While the market of IR detectors has recently been dominated by HgTe-based materials, Pb-chalcogenides have still important applications in devices like diode lasers for molecular spectroscopy and gas monitors [5], and may become a key device material for IR integrated optics and telecommunication systems [6,7]. Use of appropriate ternary alloys enables tuning the bandgap to a desired wavelength and/or tailoring the lattice constant for matching the substrate and the active epilayer lattice constant.…”