A microwave photonic filter(MPF)with reconfigurability and tunability resulting from the superposition of the transfer functions is proposed.Based on the Vernier efect between the optical frequency combs and the periodic optical filters,each comb line can be mapped into a sub-filter in the electronic field.The sub-filters are superposed to obtain the total transfer function of the MPF.By manipulating a few comb lines,we can reconfigure the passband shape,tune the bandwidth,and adjust the center frequency independently.Experiments verify that the bandwidth can be tuned from 224.8 to 674.3 MHz,and that the center frequency ranges from 1 to 4 GHz.
A backside illuminated mesa-structure In Ga As/In P modified uni-traveling-carrier photodiode(MUTC-PD) with wide bandwidth and high saturation power is fabricated and investigated. The device structure is optimized to reduce the capacitance and resistance. For the 22-μm-diameter device, the maximum responsivity at 1.55 μm is 0.5 A/W, and the 3-d B cutoff frequency reaches up to 28 GHz. The output photocurrent at the 1-d B compression point is measured to be 54 m A at 25 GHz, with a corresponding output radio frequency(RF) power of up to 15.5 d Bm. The saturation characteristics of the MUTC-PD are also verified by the electric field simulation, and electric field collapse is found to be the cause of the saturation phenomenon.
This paper presents the fundamental principles and recent advances in the field of linearity enhancement of Mach–Zehnder modulators in microwave photonic systems using all-optical signal processing.A review of the fundamentals and applications that implement the linearity improvement is also provided.
In GaN quantum dot is a promising optoelectronic material,which combines the advantages of low-dimensional and wide-gap semiconductors.The growth of In GaN quantum dots is still not mature,especially the growth by metal–organic–vapor phase epitaxy(MOVPE),which is challenge due to the lack of 、itin-situ monitoring tool.In this paper,we reviewed the development of In GaN quantum dot growth by MOVPE,including our work on growth of near-UV,green,and red In GaN quantum dots.In addition,we also introduced the applications of In GaN quantum dots on visible light emitting diodes.
In this paper,we introduce a horizontal slot in the reversed-rib chalcogenide glass waveguide to tailor its dispersion characteristics.The waveguide exhibits a flat and low dispersion over a wavelength range of 1080 nm,in which the dispersion fluctuates between-10.6 ps·nm^(-1)·km^(-1) and +11.14 ps·nm^(-1)·km^(-1).The dispersion tailoring effect is due to the mode field transfer from the reversed-rib waveguide to the slot with the increase of wavelength,which results in the extension of the low dispersion band.Moreover,the nonlinear coefficient and the phase-matching condition of the fourwave mixing process in this waveguide are studied,showing that the waveguide has great potential in nonlinear optical applications over a wide wavelength range.
GaN and AlN nanowires(NWs) have attracted great interests for the fabrication of novel nano-sized devices. In this paper, the nucleation processes of GaN and AlN NWs grown on Si substrates by molecular beam epitaxy(MBE)are investigated. It is found that GaN NWs nucleated on in-situ formed Si_3N_4 fully release the stress upon the interface between GaN NW and amorphous Si_3N_4 layer, while AlN NWs nucleated by aluminization process gradually release the stress during growth. Depending on the strain status as well as the migration ability of Ⅲ group adatoms, the different growth kinetics of GaN and AlN NWs result in different NW morphologies, i.e., GaN NWs with uniform radii and AlN NWs with tapered bases.
We propose and experimentally demonstrate a scheme of high-Q microwave photonic filter(MPF)using the techniques of self-phase modulation(SPM)spectrum broadening and third-order dispersion(TOD)com-pensation.The optical pulses from a mode-locking laser are spectrally broadened by the SPM in the highly nonlinear fiber.A wideband optical frequency comb with 365 spectral lines within 10-dB power variation from the highest spectral power is obtained.By applying a cubic phase modulation via a waveshaper,the effect of TOD which broadens the MPF passband is eliminated.The final implemented MPF has a Q-value as high as 296 and a tuning range of 700 MHz.
We present a polarization-maintaining PANDA ring-core fiber(PM-PRCF) characterized by the combination of a ring-core structure with two stress-applying rods. This special fiber design separates the adjacent modes and avoids the cutoff of the higher-order modes, which is a common problem in elliptical core polarization-maintaining few-mode fibers. Using a high-contrast index ring and stress-induced birefringence, the PM-PRCF features support for 10 vector modes, with effective refractive index separations from their adjacent modes >10^(-4).Broadband performance is investigated subsequently over a wide wavelength range from 1500 to 1630 nm.The proposed fiber is targeted at applications in space-division multiplexing while eliminating the complex multiple-input multiple-output signal processing.
