THz radiation is generated from bulk InAs shallow-incidence-angle mirror inside the cavity of a m... more THz radiation is generated from bulk InAs shallow-incidence-angle mirror inside the cavity of a mode-locked Ti:sapphire laser. The magnetic field is also applied for radiation enhancement.
For the first time, ultrafast laser annealed BEOL gate-all-around (GAA) transistor and FeFET memo... more For the first time, ultrafast laser annealed BEOL gate-all-around (GAA) transistor and FeFET memory were demonstrated with monolithic 3D near-memory-computing (NMC) circuit. The GAA MOSFETs employing ultrafast picosecond visible laser dopant activation exhibit record-high Ion (nFETs=407 uA/um, pFETs=345 uA/um). The BEOL FeFETs memory exhibits large memory window ΔVth = 1.2V, more than 106 cycle endurance. Moreover, the 3D stackability of the GAA MOSFETs and FeFET memory bit cell enable reduces the area of the NMC circuitry and improve the readout throughput.
IEEE Transactions on Terahertz Science and Technology, 2016
The enhanced broadband THz radiation excited by pre-chirping the femtosecond pumping laser pulse ... more The enhanced broadband THz radiation excited by pre-chirping the femtosecond pumping laser pulse is explored from a photoconductive antenna made by the low-temperature molecular-beam-epitaxy (LT-MBE) grown Gallium Arsenide (GaAs). Nearly 3-dB enlargement on peak amplitude of THz radiation accompanied with broadened bandwidth is achieved with positively chirped pulse excitation. The laser with short pulsewidth assists the broadening of THz bandwidth, whereas the peak intensity of THz relies strictly on lengthened carrier lifetime. The enhancement of high-frequency radiation components at low pumping intensity also indicates the nature of power dependence in such a coherently controlled process. When photocurrent saturation occurs in the LT-MBE-grown GaAs under high-power pumping condition, the clipping effect on peak amplitude of current pulse lengthens the duration of current surge effect. Both the peak intensity and the frequency spectrum of the generated THz pulse concurrently declines. The physical mechanism related to pre-chirped pulse excitation dependent carrier dynamics is proposed to elucidate the spectral response as well as the power dependence in such a coherently controlled THz radiation process.
A supercontinuum with over 420-nm of spectral bandwidth is generated in a single-modefiber pumped... more A supercontinuum with over 420-nm of spectral bandwidth is generated in a single-modefiber pumped by noise-like-pulses from an Yb-doped fiber laser. The supercontinuum source is successfully employed in a spectral-domain optical coherence tomography imaging system.
ABSTRACT We report on preliminary results on ultrafast responses and ultra-wide bandwidth of furn... more ABSTRACT We report on preliminary results on ultrafast responses and ultra-wide bandwidth of furnace-annealed multi-energy-bombarded GaAs:As + photoconductors at high bias voltage with much curtailed tail response. Further, we report THz emission characteristics of dipole antennas fabricated on GaAs:As+ in light of previous works on low temperature grown GaAs
We report the effect of annealing temperature on the near bandgap transmittance, absorption coeff... more We report the effect of annealing temperature on the near bandgap transmittance, absorption coefficient, as well as the evolution of shallow-level defects of arsenic-ion-implanted GaAs (referred as GaAs:As+) by using Fourier transform infrared spectroscopy. By either fitting the absorption curve with A(hv-Eg)1/2 or extrapolating the ((alpha) hv)2 curve to the abscissa, the blue shift of bandgap energy of RTA-annealed GaAs:As+ samples was found to increase from 1.35 eV (Ta equals 300 degrees Celsius) to 1.41 eV (Ta equals 800 degrees Celsius). The slightly perturbed absorption spectra at near bandgap region interpret that there are still a large amount of near-bandedge defects continuously distributed in the RTA-annealed GaAs:As+ samples. The diminishing of shallow-level defects with at higher annealing temperatures was also observed via the derivative absorption spectra.
We investigate femtosecond pulse transmission through BK7 in the presence of its second harmonic ... more We investigate femtosecond pulse transmission through BK7 in the presence of its second harmonic as a seeding pulse. Enhanced absorption is observed when the pulses are co-polarized. Such phenomenon can be used to control absorption.
We have studied the evolution of the pulse widths and the corresponding spectra of femtosecond op... more We have studied the evolution of the pulse widths and the corresponding spectra of femtosecond optical pulses generated by a colliding-pulse mode-locked (CPM) dye laser (λ = 620 nm) with (case I) and without (case II) compensating prisms. The build-up time to steady state took ~10 µs for case I. The peak wavelength of the corresponding spectra shifted slightly to the red as the pulses evolved. Otherwise, the spectra did not exhibit distinct features. In case II, the pulse width exhibited an oscillatory behavior and approached the steady state after a delay of ~50 µs. A dramatically changed spectrum was also observed at the first minimum of oscillation. These results were in good agreement with our proposed physical mechanisms.
We demonstrate a liquid crystal based THz spatial light modulator (SLM). Indium tin oxide or gold... more We demonstrate a liquid crystal based THz spatial light modulator (SLM). Indium tin oxide or gold finger type patterns were used for transparent (>70 % at 0.08 to 1.2 THz) conductor and self-cross polarizer. The phase shift and amplitude modulation achieved are greater than 90° and 30 % in broadband in THz frequency. This SLM could become a promising candidate for high speed THz imaging application via compress sensing algorithm
We report on the ultrahigh-resolution optical coherence tomography (OCT) with a novel high-power ... more We report on the ultrahigh-resolution optical coherence tomography (OCT) with a novel high-power supercontinuum (SC) light source generated by noise-like pulses from an Yb-doped fiber laser. The SC spectrum is flat with a bandwidth of 420 nm centered around ~1.3 μm. The light source is successfully employed in a time-domain OCT (TD-OCT), achieving an axial resolution of 2.3 μm. High resolution fiber-based spectral-domain OCT (SD-OCT) imaging of bio-tissue was also demonstrated.
THz radiation is generated from bulk InAs shallow-incidence-angle mirror inside the cavity of a m... more THz radiation is generated from bulk InAs shallow-incidence-angle mirror inside the cavity of a mode-locked Ti:sapphire laser. The magnetic field is also applied for radiation enhancement.
For the first time, ultrafast laser annealed BEOL gate-all-around (GAA) transistor and FeFET memo... more For the first time, ultrafast laser annealed BEOL gate-all-around (GAA) transistor and FeFET memory were demonstrated with monolithic 3D near-memory-computing (NMC) circuit. The GAA MOSFETs employing ultrafast picosecond visible laser dopant activation exhibit record-high Ion (nFETs=407 uA/um, pFETs=345 uA/um). The BEOL FeFETs memory exhibits large memory window ΔVth = 1.2V, more than 106 cycle endurance. Moreover, the 3D stackability of the GAA MOSFETs and FeFET memory bit cell enable reduces the area of the NMC circuitry and improve the readout throughput.
IEEE Transactions on Terahertz Science and Technology, 2016
The enhanced broadband THz radiation excited by pre-chirping the femtosecond pumping laser pulse ... more The enhanced broadband THz radiation excited by pre-chirping the femtosecond pumping laser pulse is explored from a photoconductive antenna made by the low-temperature molecular-beam-epitaxy (LT-MBE) grown Gallium Arsenide (GaAs). Nearly 3-dB enlargement on peak amplitude of THz radiation accompanied with broadened bandwidth is achieved with positively chirped pulse excitation. The laser with short pulsewidth assists the broadening of THz bandwidth, whereas the peak intensity of THz relies strictly on lengthened carrier lifetime. The enhancement of high-frequency radiation components at low pumping intensity also indicates the nature of power dependence in such a coherently controlled process. When photocurrent saturation occurs in the LT-MBE-grown GaAs under high-power pumping condition, the clipping effect on peak amplitude of current pulse lengthens the duration of current surge effect. Both the peak intensity and the frequency spectrum of the generated THz pulse concurrently declines. The physical mechanism related to pre-chirped pulse excitation dependent carrier dynamics is proposed to elucidate the spectral response as well as the power dependence in such a coherently controlled THz radiation process.
A supercontinuum with over 420-nm of spectral bandwidth is generated in a single-modefiber pumped... more A supercontinuum with over 420-nm of spectral bandwidth is generated in a single-modefiber pumped by noise-like-pulses from an Yb-doped fiber laser. The supercontinuum source is successfully employed in a spectral-domain optical coherence tomography imaging system.
ABSTRACT We report on preliminary results on ultrafast responses and ultra-wide bandwidth of furn... more ABSTRACT We report on preliminary results on ultrafast responses and ultra-wide bandwidth of furnace-annealed multi-energy-bombarded GaAs:As + photoconductors at high bias voltage with much curtailed tail response. Further, we report THz emission characteristics of dipole antennas fabricated on GaAs:As+ in light of previous works on low temperature grown GaAs
We report the effect of annealing temperature on the near bandgap transmittance, absorption coeff... more We report the effect of annealing temperature on the near bandgap transmittance, absorption coefficient, as well as the evolution of shallow-level defects of arsenic-ion-implanted GaAs (referred as GaAs:As+) by using Fourier transform infrared spectroscopy. By either fitting the absorption curve with A(hv-Eg)1/2 or extrapolating the ((alpha) hv)2 curve to the abscissa, the blue shift of bandgap energy of RTA-annealed GaAs:As+ samples was found to increase from 1.35 eV (Ta equals 300 degrees Celsius) to 1.41 eV (Ta equals 800 degrees Celsius). The slightly perturbed absorption spectra at near bandgap region interpret that there are still a large amount of near-bandedge defects continuously distributed in the RTA-annealed GaAs:As+ samples. The diminishing of shallow-level defects with at higher annealing temperatures was also observed via the derivative absorption spectra.
We investigate femtosecond pulse transmission through BK7 in the presence of its second harmonic ... more We investigate femtosecond pulse transmission through BK7 in the presence of its second harmonic as a seeding pulse. Enhanced absorption is observed when the pulses are co-polarized. Such phenomenon can be used to control absorption.
We have studied the evolution of the pulse widths and the corresponding spectra of femtosecond op... more We have studied the evolution of the pulse widths and the corresponding spectra of femtosecond optical pulses generated by a colliding-pulse mode-locked (CPM) dye laser (λ = 620 nm) with (case I) and without (case II) compensating prisms. The build-up time to steady state took ~10 µs for case I. The peak wavelength of the corresponding spectra shifted slightly to the red as the pulses evolved. Otherwise, the spectra did not exhibit distinct features. In case II, the pulse width exhibited an oscillatory behavior and approached the steady state after a delay of ~50 µs. A dramatically changed spectrum was also observed at the first minimum of oscillation. These results were in good agreement with our proposed physical mechanisms.
We demonstrate a liquid crystal based THz spatial light modulator (SLM). Indium tin oxide or gold... more We demonstrate a liquid crystal based THz spatial light modulator (SLM). Indium tin oxide or gold finger type patterns were used for transparent (>70 % at 0.08 to 1.2 THz) conductor and self-cross polarizer. The phase shift and amplitude modulation achieved are greater than 90° and 30 % in broadband in THz frequency. This SLM could become a promising candidate for high speed THz imaging application via compress sensing algorithm
We report on the ultrahigh-resolution optical coherence tomography (OCT) with a novel high-power ... more We report on the ultrahigh-resolution optical coherence tomography (OCT) with a novel high-power supercontinuum (SC) light source generated by noise-like pulses from an Yb-doped fiber laser. The SC spectrum is flat with a bandwidth of 420 nm centered around ~1.3 μm. The light source is successfully employed in a time-domain OCT (TD-OCT), achieving an axial resolution of 2.3 μm. High resolution fiber-based spectral-domain OCT (SD-OCT) imaging of bio-tissue was also demonstrated.
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