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ABSTRACT: We originally demonstrate the use of an AlGaInAs periodic quantum-well absorber to achieve a quasi-continuous-wave (QCW) diode-pumped
passively Q-switched Nd:YVO4 laser with an intracavity optical parametric oscillator (OPO). With a diode-pumping energy of 35 mJ, the output pulse energy
and the pulse width at 1573nm are found to be 1.58 mJ and 26 ns, respectively. The pulse repetition rate can be up to 100
Hz with the overall OPO beam quality M2 factor to be better than 1.5.
Applied Physics B 04/2012; 104(3):591-595. · 2.19 Impact Factor
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ABSTRACT: We demonstrate that the simultaneous self-mode-locking of TEM0,0 and TEM1,0 modes can be achieved in a standard end-pumped Nd:YVO4 laser. With this simultaneous self-mode-locking, the transverse beat frequency can be accurately measured as a function of
the absorbed power. We employ the measured beat frequency and the cavity theory to precisely determine the effective focal
length of the thermal lens in the gain medium.
Laser Physics 04/2012; 21(3):480-484. · 3.61 Impact Factor
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ABSTRACT: We thoroughly analyze the level statistics and eigenfunctions in concentric as well as nonconcentric square torus billiards. We confirm the characteristics of quantum and classical correspondence and the existence of scarred and superscarred modes in concentric square torus billiards. Furthermore, we not only verify that the transition from regular to chaotic behaviors can be manifested in nonconcentric square torus billiards, but also develop an analytical distribution to excellently fit the numerical level statistics. Finally, we intriguingly observe that numerous eigenstates commonly exhibit the wave patterns to be an ensemble of classical diamond trajectories, as the effective wavelengths are considerably shorter than the size of internal hole.
Physical Review E 02/2012; 85(2 Pt 2):026202. · 2.26 Impact Factor
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Optics Communications 01/2012; · 1.49 Impact Factor
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Applied Physics B 01/2012; · 2.19 Impact Factor
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ABSTRACT: We explore the lasing mode selection between the chaotic and scarred modes in stadium-shaped vertical-cavity surface-emitting lasers (VCSELs). Experimental results reveal that the spatial gain distribution in the active layer of a VCSEL can be modified via the aperture size to favor the generation of either the chaotic or the scarred modes. Experimentally obtained chaotic and scarred modes are further employed to perform statistical analysis of wave function intensities for making a comparison with predictions based on the nonlinear σ model. We verify that the scarring effect can be quantitatively relevant to the weak-localization correction in the intensity probability distribution.
Physical Review E 11/2011; 84(5 Pt 2):056201. · 2.26 Impact Factor
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ABSTRACT: A fully-integrated, 3-5 GHz Impulse-Radio UWB transceiver with on-chip flash ADC is designed in 90 nm-CMOS. A new scheme for receiver phase acquisition is proposed that uses pulse injection-locking to synchronize the receive clock with the transmitted data, eliminating the need for clock/data recovery (CDR), requiring only static receiver phase alignment with the transmitted pulses at startup. Transmitter pre-emphasis equalization is utilized to mitigate the effect of multipath on bit-error rate (BER). Occupying 2 mm<sup>2</sup> die area, the transceiver achieves a data rate of 500 Mbps, energy efficiency of 0.18 nj/b at 500 Mbps, and a RX raw BER of <; 10<sup>-3</sup> across a distance of 10 cm at 125 Mbps. In a real multipath environment, BER improves by 2.35× after equalization of the first multipath reflection.
IEEE Journal of Solid-State Circuits 06/2011; · 3.23 Impact Factor
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ABSTRACT: Carrierless impulse radio ultra-wideband (IR-UWB) radios have attracted significant research interest due to their low system complexity and power consumption. Unfortunately, IR-UWB systems suffer from the difficulty in controlling the transmitted spectral mask because of process, voltage, and temperature variations. In this paper, a monolithic 3-5-GHz IR-UWB transceiver is presented that integrates both amplitude and spectrum tunability, thereby providing adaptable spectral characteristics for different data rate transmission. The noncoherent receiver employs a simplified low-power merged correlator, eliminating the need for a conventional sample-and-hold circuit. After self-correlation, the demodulated data is digitally synchronized with the baseband clock. The 4 mm<sup>2</sup> 0.13 μm CMOS transmitter and receiver consume 2.2 and 13.2 mW, respectively at the data rate of 100 Mb/s. The measured peak-to-peak transmitted pulse amplitudes are 240, 170, and 115 mV, with a tunable frequency range of 3.2-4.1 GHz. The receiver exhibits a maximum gain of 70 dB, noise figure of 8.6 dB, and the input 1-dB compression point of -28 dBm . With off-chip antennas, the transceiver achieves a bit error rate of 10<sup>-3</sup> at a sensitivity of -50 dBm.
IEEE Transactions on Microwave Theory and Techniques 05/2011; · 1.85 Impact Factor
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ABSTRACT: We report that the subthreshold emission spectra of vertical-cavity surface-emitting lasers (VCSELs) can be analogously used to manifest the quantum-billiard energy spectra. The Fourier-transformed distributions of the subthreshold emission spectra are demonstrated to display various peak structures that are in good agreement with the results of the quantum-billiard model. We also verify that the statistical analyses of the nearest-neighbor eigenvalue spacing distributions obey a Poisson distribution for an equilateral-triangular device and a Wigner distribution for a stadium-shaped device.
Physical Review E 01/2011; 83(1 Pt 2):016208. · 2.26 Impact Factor
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Applied Physics B 01/2011; 103:291. · 2.19 Impact Factor
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Applied Physics B 01/2011; 103:637. · 2.19 Impact Factor
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Journal of optics 01/2011; 13:075705. · 1.57 Impact Factor
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Applied Physics B 01/2011; 103:841. · 2.19 Impact Factor
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Applied Physics B 01/2011; 105:385. · 2.19 Impact Factor
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ABSTRACT: We report on a millijoule-level Yb-doped photonic crystal fiber (PCF) laser passively Q-switched with AlGaInAs quantum wells (QWs). Three types of AlGaInAs devices with different QW numbers are fabricated to investigate the performance. With 50 groups of three AlGaInAs QWs as a saturable absorber (SA), the PCF laser generates an average power of 7.1 W with a pulse repetition rate of 6.5 kHz at a pump power of 16 W, corresponding to the pulse energy of 1.1 mJ. The maximum peak power is up to 110 kW.
Optics Express 12/2010; 18(26):27910-5. · 3.59 Impact Factor
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ABSTRACT: A single channel, loop-unrolled, asynchronous successive approximation (SAR) ADC fabricated in 40nm CMOS is presented. Compared with a conventional SAR structure that exhibits significant delay in the digital feedback logic, the proposed 6b SAR-ADC employs a different comparator for each bit of conversion, with an asynchronous ripple clock generated after each quantization. With the sample rate limited only by the six delays of the C-DAC settling and comparator quantizations, the 40nm-CMOS SAR-ADC achieves a peak SNDR of 32.9dB and 30.5dB at 1GS/s and 1.25GS/s, respectively, consuming 5.28mW and 6.08mW in a core area less than 170um × 85um.
Custom Integrated Circuits Conference (CICC), 2010 IEEE; 10/2010
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ABSTRACT: A fully-integrated, 3.1-5 GHz Impulse-Radio UWB transceiver with on-chip flash ADC is designed in 90 nm-CMOS. A new scheme for receiver phase acquisition is proposed that uses pulse injection-locking to synchronize the receive clock with the transmitted data, eliminating the need for clock/data recovery (CDR). Occupying 2 mm<sup>2</sup> die area, the transceiver achieves a maximum data rate of 500 Mbps, energy efficiency of 0.18 nJ/b at 500 Mbps, and a RX-BER of 10<sup>-3</sup> across a distance of 10 cm at 125 Mbps.
Radio Frequency Integrated Circuits Symposium (RFIC), 2010 IEEE; 06/2010
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ABSTRACT: This paper describes a quad-lane, 6.4-7.2 Gb/s serial link receiver prototype using a forwarded clock architecture. A novel phase deskew scheme using injection-locked ring oscillators (ILRO) is proposed that achieves greater than one UI of phase shift for multiple clock phases, eliminating phase rotation and interpolation required in conventional architectures. Each receiver, optimized for power efficiency, consists of a low-power linear equalizer, four offset-cancelled quantizers for 1:4 demultiplexing, and an injection-locked ring oscillator coupled to a low-voltage swing, global clock distribution. Measurement results show a 6.4-7.2 Gb/s data rate with BER < 10<sup>-12</sup> across 14 cm of PCB, and also an 8.0 Gb/s data rate through 4 cm of PCB. Designed in a 1.2 V, 90 nm CMOS process, the ILRO achieves a wide tuning range from 1.6-2.6 GHz. The total area of each receiver is 0.0174 mm<sup>2</sup>, resulting in a measured power efficiency of 0.6 mW/Gb/s.
IEEE Journal of Solid-State Circuits 05/2010; · 3.23 Impact Factor
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ABSTRACT: The properties of LDMOSFETs with dielectric material (several pieces of STI) being inserted into the drift region of the transistor to modulate the one-dimensional electric field distribution are demonstrated. Although this structure increases the turn-on resistance slightly, it also increases the breakdown voltage (BV) by a larger percentage. Systematic experimental results verify that the breakdown voltage of this device can be tuned by varying the dielectric width.
Electronics Letters 04/2010; · 0.96 Impact Factor
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ABSTRACT: Two critical aspects of sense amplifiers (SA), power consumption and clock-to-data delay, are studied and presented for operation under low-supply voltage and driven by low-swing clock. Trade-offs and simulation results are given for a 4-stack StrongARM and a 3-stack double-tail SA, showing up to 50% power reduction in the SA itself and 25% in the clock generation circuit, with acceptable delay degradation.
Circuits and Systems, 2009. ISCAS 2009. IEEE International Symposium on; 06/2009
