In this paper, a reconfigurable photonic bandpass RF filter employing a semiconductor optical amplifier (SOA) and an
Opto-VLSI processor is proposed where a high coherent RF modulated laser carrier is fed into the SOA and through
cross-gain modulation, a low coherence RF-modulated amplified spontaneous emission (ASE) can be generated. By
spectrally slicing the ASE with an optical comb filter, RF-modulated wavebands of different centre wavelengths are
generated. These RF-modulated wavebands are then processed by an Opto-VLSI processor which arbitrarily shapes the
intensity profile of the wavebands. A high-dispersion optical fibre introduces linear true-time delays between the
different wavebands so that after photodetection a photonic bandpass RF filter with multiple taps is realised. The proof-of-
concept of the photonic bandpass filter is experimentally demonstrated, and results show that the filter can operate at
3.6 GHz with more than 25 dB rejection and its working frequency can be tuned by reconfigurable holograms generated
by the Opto-VLSI processor. The filter can work with the laser carrier wavelength in the range of 1523nm to 1566nm
without any optical coherence noises.
The ability of a liquid-crystal spatial light modulator (LC-SLM) to generate lens and lens arrays of variable focal lengths
and selectable fields of view (FOV) makes them excellent candidates for many adaptive optics applications including
free-space optical telecommunications, astronomy and retinal imaging. In this paper, we report a range of dynamic lens
and lens array designs and optimization using a LC-SLM as an adaptive Hartmann-Shack wavefront sensor. The
measured wavefront aberration is reconstructed using Zernike polynomials through the application of its conjugated
wavefront onto the LC-SLM to achieve dynamic wavefront detection and correction. Computer algorithms based on
Fourier transformation for lens synthesis have been developed to address the LC-SLM and to generate appropriate phase
holograms that emulate lens and/or lenslet arrays with programmable focal lengths, tilting angles and diameters. The
classic least-square (LS) method is used to determine the Zernike polynomial coefficients for the reconstruction of the
aberrated wavefront. Experimental results demonstrate the dynamic generation of lens arrays of variable focal lengths.
We also experimentally characterize the phase modulation performance and wavefront generation performance of the
LC-SLM through the application of Zernike functions and as diffractive optical elements (DOEs) for dynamic wavefront
Reconfigurable multi-channel optical filters are presented in this paper. The operation principle of the reconfigurable filter is based on the dynamic beam steering capacity of Opto-VLSI processor in conjunction with a high dispersion free space grating. The dispersion grating separates the input signal spectrum while the Opto-VLSI processor is driven by optimised phase holograms to dynamically select the wavelengths to be coupled into the output port. Experimental results show that up to 8 bands can be synthesised, with a wavelength tuning span of 10 nm and a 3dB bandwidth less than 0.5nm.
In this paper, a novel reconfigurable 5-tap photonic RF filter based on Opto-VLSI processor is proposed where an Opto-VLSI processor is used in conjunction with a 5-fibre Bragg grating (FBG) array to slice the spectrum of a broad band light source, thus achieving commensurate true-time delays and variable tap weights. The proposed photonic RF filterstructure is experimentally demonstrated by means of several examples which show the capability of the Opto-VLSI processor to synthesise transversal RF filter responses with adaptive weights.
213nm Solid-state laser technology provides an alternative method to replace toxic excimer laser in LASIK system. In this paper, we report a compact fifth harmonic generation system to generate high pulse energy 213nm laser from Q-switched Nd:YAG laser for LASIK application based on three stages harmonic generation procedures. A novel crystal housing was specifically designed to hold the three crystals with each crystal has independent, precise angular adjustment structure and automatic tuning control. The crystal temperature is well maintained at ~130°C to improve harmonic generation stability and crystal operation lifetime. An output pulse energy 35mJ is obtained at 213nm, corresponding to total conversion efficiency ~10% from 1064nm pump laser. In system verification tests, the 213nm output power drops less than 5% after 5 millions pulse shots and no significant damage appears in the crystals.
In this paper, a MicroPhotonic-based high-Q tunable RF filter architecture is proposed. The architecture uses a Vertical Cavity Surface Emitting Laser (VCSEL) array, a 2D ultra-wideband photo-receiver array and a multi-cavity optical substrate to generate a large number of optical true-time delays thus achieving arbitrary, high-resolution RF filter transfer characteristics. By tuning the responses of the different optical cavities, adaptive high-Q RF filter characteristics can be realized over a wide RF frequency range. Proof-of-concept experimental results demonstrate the adaptability of the MicroPhotonic-based RF filter.
In this paper we present and demonstrate a dynamic lens and lens array generation method with programmable focal length based on an Opto-VLSI processor. The Opto-VLSI is driven by computer generated algorithm to generate a discrete Fresnel lens phase hologram. By optimizing the phase hologram, lenses and lens arrays of different focal lengths ranging from 300mm to infinity can be realized. The optical axis of each lens element can be independently addressed to simultaneously focus and steer an optical beam within an angular range of ±0.5°.
MicroPhotonic broadband RF signal processors utilize the capability of photons to perform true-time delay processing at very low loss that is unattainable by conventional electronic methods. In this paper, we present a novel MicroPhotonic interference mitigation filter architecture that utilises a CMOS Si photoreceiver/VCSEL array in conjunction with a true-time-delay multi-cavity optical substrate to realise an adaptive transversal RF processor with arbitrary response. Results show that the proposed MicroPhotonic structure can synthesize adaptive interference mitigation with a shape factor (ratio of the -40<i>dB</i> bandwidth to the -3<i>dB</i> bandwidth) as low as 2 and passband ripples less than 0.25<i>dB</i>.