Dynamically Tunable Terahertz Emission Enabled by Anomalous Optical Phonon Responses in Lead Telluride
- SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Argonne National Lab. (ANL), Lemont, IL (United States)
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Duke Univ., Durham, NC (United States)
- SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States)
Lead telluride (PbTe), a narrow bandgap semiconductor commonly used in infrared detectors, exhibits anomalous vibrational and structural properties, making it appealing for thermoelectrics. Despite significant fundamental interest in the microscopic origins of its unusual vibrational properties, the optical functionalities stemming from phonons and electronphonon coupling in PbTe have not been closely investigated. This paper reports measurements of terahertz (THz) radiation from a PbTe single crystal following ultrafast optical excitation and investigates IR-active phonon responses as a function of excitation fluence and temperature. We uncover a spectrally tunable THz emission peak enabled by an epsilon-near-zero response of the coupled plasmon-longitudinal optical phonon mode that can be dynamically shifted via tuning photocarrier density. Spectral tunability (Delta omega/omega = 25%) is significant and beyond what has been achieved by any other THz emitter. In addition, the emitted THz fields reveal signatures of a zone center transverse optical phonon anomaly and unveil a new mode at 0.3 THz that diminishes in amplitude under increasing photocarrier density. Temperature-dependent measurements suggest that the transverse-like modes at 1 and 1.5 THz are possibly of different origins. These results indicate that the unusual phononic properties in PbTe are tunable via photoexcitation and enable new optical functionalities in THz applications, such as spectrally tunable emitters and all-optical modulators.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
- Grant/Contract Number:
- AC02-76SF00515; AC02-06CH11357
- OSTI ID:
- 1873399
- Alternate ID(s):
- OSTI ID: 1897904
- Journal Information:
- ACS Photonics, Vol. 8, Issue 12; ISSN 2330-4022
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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