Browsing by Author "Tani, M"

Now showing 1 - 11 of 11

Control of enhanced THz transmission through metallic hole arrays using nematic liquid crystal
(2005-05-30)
Pan, CL
;
Hsieh, CF
;
Pan, RP
;
Tanaka, M
;
Miyamaru, F
We demonstrate frequency tuning of enhanced THz radiation transmitted through a two- dimensional metallic hole array ( 2D- MHA) by controlling the index of refraction of the medium filling the holes and adjacent to the 2D- MHA on one side. The medium is a nematic liquid crystal ( NLC) and its index of refraction is varied using magnetically controlled birefringence of the NLC. With the NLC, the peak transmission frequency of the 2D- MHA shift to the red by 0.112 THz and can be tuned from 0.193 to 0.188 THz. The peak transmittance is as high as 70% or an enhancement of 2.42 times, considering the porosity of the 2D- MHA. As a tunable THz filter, this device exhibits a continuous tuning range of 4.7 GHz, a low insertion loss of 2.35 to 1.55 dB and a quality factor of similar to 4- 5. (C) 2005 Optical Society of America.
Control of THz transmission through two-dimensional metallic photonic crystals
(2005)
Pan, CL
;
Hsieh, CF
;
Pan, RP
;
Tanaka, M
;
Miyamaru, F
We demonstrate frequency tuning of resonantly enhanced THz radiation transmitted through a two-dimensional metallic photonic crystal on a liquid crystalline "substrate".
Dark current and trailing-edge suppression in ultrafast photoconductive switches and terahertz spiral antennas fabricated on multienergy arsenic-ion-implanted GaAs
(2005-07-01)
Liu, TA
;
Lin, GR
;
Lee, YC
;
Wang, SC
;
Tani, M
We report ultrafast (similar to 2.7 ps, instrument limited) switching responses of a multienergy- implanted GaAs:As' photoconductive switches (PCSs) with suppressed trailing edge and reduced dark. current. This material is highly resistive with dark current as low as 0.94 mu A at a bias of 40 V. The carrier mobility of the former is similar to 590 cm(2)/V s, resulting in a small-signal optical responsivity of similar to 2 mA/W. Pumped at 100 mW and biased at 80 V, the multienergy-implanted GaAs: As+ PCS exhibits peak response (0.35 V) comparable to the best result of single-energy-implanted ones. The improvement on photoconductive response is crucial for the generation of shorter terahertz emission pulses from spiral antennas fabricated on multienergy-implanted GaAs:As+ (0.8 ps) than single-energy-implanted GaAs (1.2 ps), with the central frequency blueshifted to 0.2 THz (from 0.15 THz) and the spectral bandwidth broadened to 0.18 THz (from 0.11 THz). (c) 2005 American Institute of Physics.
Generation of coherent cw-terahertz radiation using a tunable dual-wavelength external cavity laser diode
(1999-11-01)
Gu, P
;
Chang, F
;
Tani, M
;
Sakai, K
;
Pan, CL
A tunable dual-wavelength external cavity laser diode (2-lambda-ECL) was used to generate tunable coherent cw-terahertz (THz) radiation by photomixing in a biased photoconductive antenna fabricated on a low-temperature-grown (LTG)-GaAs film. The 2-lambda-ECL oscillated at the two output modes simultaneously with a frequency separation from 250 GHz to 2.1 THz in the same cavity. We demonstrated that the frequency of the emitted THz radiation corresponded to the difference frequency between the two modes of the diode laser. The tunable 2-lambda-ECL, due to its compact design and ease of optical alignment, is a promising laser source for the generation of tunable cw-THz radiation by photomixing.
Multi-energy arsenic-ion-implanted GaAs photoconductors for ultrafast switching and THz Generation
(2000)
Pan, CL
;
Liu, TA
;
Lin, GR
;
Tani, M
;
光電工程學系
Terahertz field detection beyond 30 THz by proton-bombarded InP photoconductive antennas
(2005)
Liu, TA
;
Tani, M
;
Nakajima, M
;
Hangyo, M
;
Sakai, K
We show that photoconductive antennas fabricated on proton-bombarded InP (InP:H+) substrates with a proton dosage of 1x10(15) ions/cm(2) are promising for THz detection.
THz emission characteristics of dipole antennas fabricated on multi-energy arsenic-ionimplanted GaAs and semi-insulating GaAs
(2003)
Liu, TA
;
Tani, M
;
Lin, GR
;
Pan, CL
;
光電工程學系
We compare the performance of THz dipole antennas fabricated on Multi-energy arsenic-ion-implanted GaAs (multi-GaAs:As+) and Semi-insulating (S. I.) GaAs. High damage threshold biasing (> 60 kV/cm) and large saturating optical pumping power (> 30 mW) for multi-GaAs:As+ based devices are reported.
THz emission characteristics of photoconductive antennas with different gap size fabricated on arsenic-ion-implanted GaAs
(2001)
Liu, TA
;
Tani, M
;
Lin, GR
;
Pan, CL
;
光電工程學系
Significant difference in temporal and spectral characteristics of THz radiation emitted by large- (1 mm) and small- (5mum) aperture dipole antennas fabricated on arsenic-ion-implanted GaAs and undoped semi-insulating GaAs is reported and attributed to the geometry of the antenna.
THz radiation emission properties of multienergy arsenic-ion-implanted GaAs and semi-insulating GaAs based photoconductive antennas
(2003-03-01)
Liu, TA
;
Tani, M
;
Pan, CL
;
光電工程學系
;
Department of Photonics
We compare the performance of THz photoconductive (PC) emitter antennas fabricated on multienergy arsenic ion implanted GaAs (multi-GaAs:As+) and semi-insulating GaAs. High damage threshold biasing (>60 kV/cm) and large saturation optical-pumping power (similar to20 mW) for multi-GaAs:As+ based PC antennas are reported. Carrier mobility in the As ion implanted layer of GaAs:As+ was estimated to be about 150 cm(2)/V/s, which was comparable to that of. low,temperature GaAs. (C) 2003 American Institute of Physics.
Ultrabroadband terahertz field detection by photoconductive antennas based on multi-energy arsenic-ion-implanted GaAs and semi-insulating GaAs
(2003-08-18)
Liu, TA
;
Tani, M
;
Nakajima, M
;
Hangyo, M
;
Pan, CL
The photoconductive antennas based on multi-energy arsenic-ion-implanted GaAs and semi-insulating GaAs are demonstrated to have a useful bandwidth beyond 20 THz for a gating laser pulse width of 15 fs. The bandwidth and signal-to-noise ratio are compared with those of reference photoconductive antennas based on low-temperature grown GaAs. (C) 2003 American Institute of Physics.
Ultrabroadband terahertz field detection by proton-bombarded InP photoconductive antennas
(2004-06-28)
Liu, TA
;
Tani, M
;
Nakajima, M
;
Hangyo, M
;
Sakai, K
Photoconductive ( PC) antennas fabricated on InP bombarded with 180 keV protons of different dosages (InP:H+) all exhibit a useful bandwidth of about 30 THz, comparable to that of the LT-GaAs PC antenna. The peak signal current of the best InP: H+ device (dosage of 10(15) ions/cm(2)) is slightly higher than that of the LT-GaAs one, while the signal-to-noise ratio (SNR) of the former is about half of that of the latter due to lower resistivity. This suggests that InP: H+ can be a good substrate for THz PC antennas with proper annealing and/or implantation recipe. (C) 2004 Optical Society of America.