Photonic Frequency Up-conversion Research Articles

Dual-band pixelless upconversion imaging devices

We have proposed a type of mid-infrared (MIR) and far-infrared (FIR) dual-band imaging device, which employs the photon frequency upconversion concept in a GaN/AlGaN MIR and FIR dual-band detector integrated with a GaN/AlGaN violet light emitting diode. On the basis of the photoresponse of single-period GaN/AlGaN dual-band detectors, we present the detailed optimization of multiperiod GaN emitter/AlGaN barrier detectors and their applications to dual-band pixelless upconversion imaging. Satisfying images have been received through the analysis of the modulation transfer function and the upconversion efficiency in the GaN/AlGaN dual-band pixelless upconverters, which exhibit good image resolution, high quantum efficiency, and negligible cross talk.

Photonic Frequency Upconversion by SBS-Based Frequency Tripling

We describe a photonic frequency upconversion by the stimulated Brillouin scattering (SBS)-based frequency tripling method. The frequency tripling and the photonic frequency upconversion are simultaneously obtained by incorporating a dual-electrode electrooptic modulator (EOM) and a single optical source. Each electrode of the dual-electrode EOM is driven by both an intermediate frequency (IF) and a microwave radio frequency (RF) signal, respectively, along with the optical frequency tripling scheme. The dual-electrode EOM generates appropriate optical sidebands, while the IF signal is conveyed by the pump signal. After the successive SBS shifting process, one of the third optical sidebands is amplified by the narrow gain spectrum of SBS. The carrier signal at 32.493 GHz with narrow linewidth, which is amplified by 20 dB while the other signals are suppressed more than 20 dB, is obtained after photodetection. From the simultaneous frequency upconversion and tripling, an IF signal at 1 GHz is upconverted around the 32.493-GHz signal, which is tripled from the RF signal (10.831 GHz). To verify the ability of conveying broadband data that is limited in the previous method based on SBS, the upconversion of a pilot tone at 1 GHz is demonstrated, which means that the data rate exceeds 1 Gb/s. The proposed photonic frequency upconversion shows the spurious free dynamic range of 75.1 dBldrHz2/3 , which is suitable for a wireless personal communication system adopting the analog fiber-optic link.

Photonic Frequency Upconversion Based on Stimulated Brillouin Scattering

We demonstrate a method of photonic frequency upconversion useful in radio-over-fiber systems, which is based on Brillouin selective amplification. One of the optical sidebands generated from the applied radio-frequency carrier at 10.831GHz is selected and amplified by Brillouin gain. By carrying the 1-GHz intermediate-frequency (IF) signal on the optical carrier and beating them with the amplified sideband, the IF signal of 1 GHz is upconverted to 11.831 GHz. This scheme can also be applied to the IF signal with bandwidth larger than the Brillouin gain bandwidth. The upconverted 11.831-GHz signal has the phase noise of -83.3dBc/Hz at 10-kHz offset. Also, the proposed upconversion scheme shows the spurious-free dynamic range of 89.5 dBmiddotHz2/3

Far-infrared upconversion imaging devices: Imaging characteristics and quantum efficiency

We have carried out an investigation of imaging characteristics and quantum efficiency of far-infrared (FIR) semiconductor imaging devices. The realization of the FIR imaging employs the concept of photon frequency upconversion in GaAs homojunction interfacial work-function internal photoemission (HIWIP) FIR detectors integrated with GaAs∕AlGaAs near-infrared light-emitting diodes (LEDs). Satisfying images have been expected through the analysis of modulation transfer function of the system, where the FIR detector parameters play key roles in the low spatial frequency image contrast, while those of LEDs dominate in the high spatial frequency range. We have examined in detail the dependence of the quantum efficiency on the emitter layer number, thickness, doping concentration, and applied bias of the FIR detectors, as well as the active layer thickness and internal quantum efficiency of the LEDs. The present study has also yielded an optimal structure for the integrated HIWIP-LED FIR imaging devices.

A photonic up-converter for a WDM radio-over-fiber system using cross-absorption modulation in an EAM

A photonic frequency up-converter with a wide wavelength bandwidth is demonstrated. The up-converter is based on wavelength conversion by cross-absorption modulation in an electroabsorption modulator. A two-tone measurement is performed to investigate the linearity of the proposed up-converter. Moreover, its dependence on the wavelength and bias voltage are found to be suitable for wavelength-division-multiplexing-based radio-over-fiber application. The proposed up-converter has a spurious free dynamic range larger than 73.8 dB/spl middot/Hz /sup 2/3/ throughout the 30-nm range of the local oscillator wavelength. Also, the up-converted signal at 26 GHz has a phase noise of -76.8 dBc/Hz at a 10-kHz offset.

Pixelless infrared imaging utilizing a p-type quantum well infrared photodetector integrated with a light emitting diode

We present experimental results which support a recently proposed scheme for infrared imaging through the combined use of a photon frequency up-conversion device with a charge coupled device (CCD) camera. The epitaxial device consists of a long wavelength p-type GaAs/AlGaAs quantum well infrared photodetector (QWIP) on top of which is grown a shorter wavelength InGaAs/GaAs light emitting diode (LED). Upon long wavelength infrared excitation of the QWIP, near infrared light is generated by the LED whose output is directed towards a commercial CCD array where the up-converted image of the long wavelength infrared source object is formed.

Pixelless infrared imaging device

A new concept for infrared imaging using a pixelless photon frequency up-conversion device together with a CCD array is presented. The concept is applicable to wavelengths longer than the CCD response range (longer than about 1.1 /spl mu/m). Preliminary imaging results using a quantum well infrared photodetector integrated with a light emitting diode are also presented.