P. Johnson

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Publications (2)2.19 Total impact

  • Article: High-gain low-noise mid-infrared quantum cascade optical preamplifier for receiver
    Huanlin Zhang, A. Seetharaman, P. Johnson, Guipeng Luo, H.Q. Le
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    ABSTRACT: Optical preamplifier (OPA) in the mid-infrared can boost weak signals in systems such as lidars or optical wireless links to improve the receiver sensitivity. Quantum-cascade-based traveling-wave OPA with off-normal Bragg-grating (BG) coupled surface-emitting configuration have been developed with a net small-signal gain up to 13 dB over a spectral range ∼70 nm around 4.7 μm, limited by the wafer gain bandwidth, and the linear dynamic range was >20 dB. Amplified spontaneous emission (ASE) was measured and the spontaneous emission factor was determined N<sub>sp</sub>∼1, indicating near quantum-limit noise behavior. Surface-emitting BG devices yielded diffraction-limited output beam, and provided simultaneous wavelength dispersion and ASE filtering. The OPA was coupled with a detector to form a receiver that is polarization-selective, has a net gain 8-13 dB with a corresponding optical filter bandwidth 25-50 GHz. These results suggest that BG-coupled OPA receivers can be useful for multispectral/wavelength-division-multiplexing systems in free space applications.
    IEEE Photonics Technology Letters 02/2005; · 2.19 Impact Factor
  • Conference Proceeding: Grating-coupled surface emitting quantum cascade semiconductor optical pre-amplifier
    H.L. Zhang, G.P. Luo, A. Seetharaman, P. Johnson, H.Q. Le
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    ABSTRACT: A grating-coupled surface-emitting mid-IR optical pre-amplifier was fabricated from a quantum cascade laser wafer and demonstrated >15-dB small signal gain with ASE power <-44 dBm. The Bragg grating served as output-coupler, ASE-filter, and wavelength division multiplexer.
    Lasers and Electro-Optics, 2004. (CLEO). Conference on; 06/2004
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