High-gain low-noise mid-infrared quantum cascade optical preamplifier for receiver

• Published in: IEEE photonics technology letters Vol. 17; no. 1; pp. 13 - 15
• Main Authors: Huanlin Zhang, Seetharaman, A., Johnson, P., Guipeng Luo, Le, H.Q.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.01.2005; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplification; Amplified spontaneous emission (ASE) filter; Bandwidth; Bragg-grating (BG) coupler; Dynamic range; Gain; Laser radar; mid-infrared (mid-IR) optical preamplifier (OPA); mid-infrared (mid-IR) receiver; multispectral/wavelength-division multiplexing (WDM); Noise levels; Optical filters; Optical receivers; Optical sensors; Optical surface waves; Preamplifiers; quantum cascade (QC); Receivers; Space applications; Spontaneous emission; surface emitting; Wireless sensor networks
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2004.837478

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 /spl sim/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//spl sim/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.