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Abstract Radiofrequency (RF) injection locking and spectral broadening of a terahertz (THz) quantum‐cascade vertical‐external‐cavity surface‐emitting laser (QC‐VECSEL) is demonstrated. An intracryostat VECSEL focusing cavity design is used to enable continuous‐wave lasing with a cavity length over 30 mm, which corresponds to a round‐trip frequency near 5 GHz. Strong RF current modulation is injected to the QC‐metasurface electrical bias to pull and lock the round‐trip frequency. The injection locking range at various RF injection powers is recorded and compared with the injection locking theory. Moreover, the lasing spectrum broadens from 14 GHz in free‐running mode to a maximum spectral width around 110 GHz with 20 dBm of injected RF power. This experimental setup is suitable for further exploration of active mode‐locking and picosecond pulse generation in THz QC‐VECSELs.
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Broadband metasurface design for terahertz quantum‐cascade VECSEL
A broadband active metasurface is designed around quantum‐cascade (QC) gain material for use in a broadband tunable QC vertical external‐cavity surface‐emitting laser (VECSEL). The metasurface is based on a unit cell containing two resonant waveguide elements that couple with the periodicity of the metasurface to produce a multi‐resonant reflection spectrum. Simulated reflectance spectra exhibit full‐width half‐maximum bandwidths up to 50% of the centre frequency. The tested QC‐VECSEL demonstrates up to 15 mW of peak pulse power at 77 K and supports multimode lasing from 2.85 to 3.9 THz (>30% fractional bandwidth around 3.37 THz). The frequency coverage is limited by how short the cavity can be made, rather than the metasurface bandwidth. Consistent multimoding results from non‐uniform distribution of spectral energy across the surface.
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- Award ID(s):
- 1711892
- PAR ID:
- 10570610
- Publisher / Repository:
- DOI PREFIX: 10.1049
- Date Published:
- Journal Name:
- Electronics Letters
- Volume:
- 56
- Issue:
- 23
- ISSN:
- 0013-5194
- Format(s):
- Medium: X Size: p. 1264-1267
- Size(s):
- p. 1264-1267
- Sponsoring Org:
- National Science Foundation
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