Mid-infrared transmission imaging and spectroscopy with PbSnTe laser diodes grown with stoichiometry-controlled liquid-phase epitaxy

• A PbSnTe/PbTe double-hetero laser structure was fabricated using TDM-CVP LPE.
• Lasing and wavelength tuning of the fabricated LD were achieved.
• Mid-IR images of benzoic acid and Si wafers were obtained.
• Absorbance peaks of organic materials were observed in the resulting spectra.

Bi- or In-doped n-PbTe/p-PbSnTe/Tl-doped p-PbTe double-hetero (DH) diode structures were fabricated using the temperature difference method under controlled vapour pressure (TDM-CVP) liquid-phase epitaxy (LPE). We fabricated a PbSnTe/PbTe DH-junction laser diode (LD) using TDM-CVP LPE and subsequently obtained sharp lasing spectra between 7.2 (1390 cm−1) and 9.4 μm (1070 cm−1) by varying the ambient temperature of the diode. When the fabricated Pb0.89Sn0.11Te/PbTe LD was used to image Si wafers with different resistivities, we obtained a clear contrast between the wafers. We also obtained the mid-infrared imaging spectrum of benzoic acid (BA) using the fabricated Pb0.89Sn0.11Te/PbTe LD, and the absorbance image obtained using the fabricated LD showed good agreement with a Fourier transform infrared (FTIR) spectrum. We observed sharp lasing spectra between 7.20 (1390 cm−1) and 7.80 μm (1280 cm−1) by varying the ambient temperature of the diode sample. We observed some absorption peaks in the obtained infrared absorption spectra of para-nitrobenzoic acid (PNBA) and BA; a peak at approximately 7.45 μm (1345 cm−1) in the spectrum of PNBA originated from NO2 symmetric stretching bands. Moreover, we observed that the other peaks in these spectra also match peaks from conventional FTIR spectra.