2020 Opto-Electronics and Communications Conference (OECC), 2020
Distributed feedback (DFB) lasers are popular light source in high-speed optical access networks;... more Distributed feedback (DFB) lasers are popular light source in high-speed optical access networks; however, the production yield is generally low due to threshold degeneracy from uniform gratings. In this work a holographic-defined two-layer moiré grating structure is utilized to provide a quarter-wavelength phase shift in DFB lasers. In experiments, 200-μm-long DFB lasers exhibit excellent single-wavelength operating behavior (SMSR > 42 dB) in terms of Bragg wavelength, high-speed modulation capability (f3dB = 22 GHz), and high device yield of 86% from 320 laser dies.
2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2017
Nonlinear wavelength generations by using the optical waveguides are more compact, low cost, and ... more Nonlinear wavelength generations by using the optical waveguides are more compact, low cost, and efficient than using the traditional solid state systems [1], and the generated broadband light sources can be utilized in optical coherence tomography, frequency metrology, optical communications, and many other. In this work, the high quality of tantalum pentoxide (Ta<inf>2</inf>O<inf>5</inf>) micro-ring resonator has been fabricated to realize the low power parametric frequency conversion in the communication region. Figure 1 shows the illustration and scanning electron microscope (SEM) image of Ta<inf>2</inf>O<inf>5</inf> based micro-ring resonator. The width/height of the ring waveguides is set as 1.5μm/0.7μm for the anomalous dispersion, which is a key element to minimize the phase mismatch in the parametric frequency conversion process. By fitting the transmission spectrum of the Ta2O5 ring resonator, the load quality factor is ∼5000...
In this study, we propose and demonstrate the enhancement of impurity-free vacancy diffusion (IFV... more In this study, we propose and demonstrate the enhancement of impurity-free vacancy diffusion (IFVD) quantum well intermixing (QWI) using supercritical fluid (SCF) treatment for photonic integration. Using an InGaAsP-based multiple quantum well (MQW) template for local bandgap engineering, SCF CO 2 with H 2 O 2 on a patterned SiO x capping layer could lower the QWI temperature to get a constant wavelength blueshift. Higher oxygen concentration was found in SiO x through high diffusivities and pressures of SCF and dehydration, enabling highly activated Ga 2 O 3 reactions for more vacancies. Additionally, different schemes of semiconductor optical amplifier (SOA)-integrated electroabsorption modulators (EAM) were fabricated. SCF treatment could realize a 9-and 6-dB improvement in extinction ratio and gain, respectively, and then high-speed 45Gb/s modulation, greatly reducing the common issue of p-type dopant (zinc) diffusion during QWI.
A new quantum well, namely InGaAsP/InAlGaAs, is used for electroabsorption modulator. High band-o... more A new quantum well, namely InGaAsP/InAlGaAs, is used for electroabsorption modulator. High band-offset ratio between well and barrier induces strong exciton effect, leading to low fiber-to-fiber loss of -8dB, >25dB extinction ratio, and >30GHz bandwidth.
CLEO/Pacific Rim 2003. The 5th Pacific Rim Conference on Lasers and Electro-Optics (IEEE Cat. No.03TH8671), 2003
We proposed a novel waveguide structure for electroabsorption modulator. By selective undercut et... more We proposed a novel waveguide structure for electroabsorption modulator. By selective undercut etching the active region, the doped conducting layers can be separated. The calculation shows that it has the properties of lower microwave loss, higher microwave speed and higher optical coupling efficiency compared with conventional ridge type.
A low-loss and high-Q Ta 2 O 5 based micro-ring resonator is presented. The micro-ring resonator ... more A low-loss and high-Q Ta 2 O 5 based micro-ring resonator is presented. The micro-ring resonator and channel waveguide with core area of the 700 by 400 nm 2 were fabricated on amorphous Ta 2 O 5 thin films prepared by reactive sputtering at 300°C and post annealing at 650°C for 3 hours. The Ta 2 O 5 micro-ring resonator with a diameter of 200 μm was coupled to the channel waveguide with a coupled Q up to 38,000 at a 0.9 μm coupling gap. By fitting the transmission spectrum of the resonator, the extracted loss coefficient inside the ring cavity and transmission coefficient of TE mode were 8.1dB/cm and 0.9923, leading to the estimated unloaded Q of higher than 44,000. In addition, based on the cutback method, the propagation loss and the coupling loss of Ta 2 O 5 channel waveguide with an inverse taper were 1.5dB/cm and 3.2 dB, respectively. The proposed Ta 2 O 5 technology offers an unique alternative for fabricating high performance guided wave devices, and may well lead to novel applications in photonic integrated circuits.
A degenerate four-wave-mixing (FWM) operation in the Ta<sub>2</sub>O<sub>5</... more A degenerate four-wave-mixing (FWM) operation in the Ta<sub>2</sub>O<sub>5</sub> submicrometer channel waveguide has been successfully demonstrated. The propagation loss of 1.5 dB/cm and total insertion loss of 5.1 dB are realized in a 12.6 mm long waveguide with inverse taper structure. The wavelength and quadratic pumping power-dependent measurements on optical transmission confirm FWM performance and characterize the nonlinearity of waveguide. The conversion efficiency of -50 dB at coupled pump power of 40 mW is observed, suggesting that the nonlinear refractive index of Ta<sub>2</sub>O<sub>5</sub> waveguide at 1550 nm is estimated to be 1×10<sup>-14</sup> cm<sup>2</sup>/W. Our primary results indicate that the…
Using a single cascaded EAM, we demonstrate 13.5-Gbps IM/DD-OFDM transmission over 0~200-km witho... more Using a single cascaded EAM, we demonstrate 13.5-Gbps IM/DD-OFDM transmission over 0~200-km without distance-dependent bit-loading. Dispersion-induced fading and nonlinear distortion in conventional IM/DD systems are settled by novel single-sideband modulation and SSII cancellation schemes, respectively.
A novel scheme of all-optical pattern free 2R regeneration is demonstrated through monolithically... more A novel scheme of all-optical pattern free 2R regeneration is demonstrated through monolithically integration of EAM and SOA. In comparison to Back-to-back case, a clearer 40 Gb/s eye-diagram with 2 dB improvement is obtained.
ABSTRACTWe have developed thin film heaters/sensors that can be integrated on top of superlattice... more ABSTRACTWe have developed thin film heaters/sensors that can be integrated on top of superlattice microcoolers to measure the Seebeck coefficient perpendicular to the layer. In this paper, we discuss the Seebeck coefficients of InGaAs/InAlAs superlattices grown with Molecular Beam Epitaxy (MBE) that have different doping concentrations, varying between 2e18, 4e18, and 8e18 to 3e19 cm−3. It was interesting to find out that – contrary to the behavior in bulk material – the Seebeck coefficient did not decrease monotonically with doping concentration. A preliminary theory of thermoelectric transport in superlattices in the regime of miniband formation has been developed to fit the experimental results. The miniband formation could enhance the thermoelectric power factor (Seebeck coefficient square times electrical conductivity) and thereby improve the Figure of merit, ZT. With this improvement, InGaAs/InAlAs superlattice microcooler become a promising candidate for on-chip temperature c...
2020 IEEE 15th International Conference on Solid-State & Integrated Circuit Technology (ICSICT)
This investigation demonstrates a high-accuracy bidirectional high-voltage (HV) current sensor fa... more This investigation demonstrates a high-accuracy bidirectional high-voltage (HV) current sensor fabricated by CMOS technology. Besides Noise filter, Sense stage, and Controller, the proposed current sensor is featured with a Switching Network composed of transmission gates, which is able to steer the direction of the current. A digital feedback loop comprises Controller generating a pair of digital signals to Switching Network such that the direction of the current is detected real time. The area of the proposed sensor on silicon is 1173x664 um 2 using 0.5 um high-voltage CMOS process, which is very compact to be easily integrated in any portable devices demanding a current monitoring function. The sensing voltage error is 0.7 % by the physical measurements, where the input voltage range is 8~14 V, and the current sensing range is-3~3 A.
An optical modulation scheme by saturating SOA-integrated EAM is used for enhancing high-speed op... more An optical modulation scheme by saturating SOA-integrated EAM is used for enhancing high-speed optical waveform. The saturation conditions on devices will have complemental carrier dynamics, thus leading to significant improvement of extinction ratio and also signal-to-noise ratio.
A negative frequency chirp- and amplitude- compensation in long-distance optical fiber transmissi... more A negative frequency chirp- and amplitude- compensation in long-distance optical fiber transmission by using SOA-integrated EAM have been demonstrated. Data transmission of 36Gb/s 16-QAM OFDM signal with 10.5GHz bandwidth over a 100km single mode fiber.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2009
In multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, the m... more In multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, the multipath components whose delays exceed cyclic prefix (CP) cause inter-symbol interference (ISI) and inter-carrier interference (ICI), which may degrade system performance severely. In this paper, we propose a joint channel estimation and ISI/ICI cancellation scheme in which a limited CP is used in a trade-off against high-rate performance in MIMO-OFDM systems. A channel estimation scheme based on the criterion of Expectation-Maximization (EM) algorithm can be proposed through the use of a training symbol. The EM algorithm uses an iterative procedure to estimate channel parameters and can estimate channel impulse response (CIR) accurately enough to mitigate ISI/ICI influences. Through the accurate CIR estimation, an efficient method has been developed to counteract ISI/ICI influences in signal detection in the case where the inserted CP length is less than the CIR length. Simulation results show that the proposed method can significantly enhance the overall MIMO-OFDM system performance after only a few iterations.
IEEE Journal of Selected Topics in Quantum Electronics, 2001
We report on the fabrication and operation of the first electrically pumped 1.55-m vertical-cavit... more We report on the fabrication and operation of the first electrically pumped 1.55-m vertical-cavity laser array for wavelength-division-multiplexing applications. The array consisted of four channels operating between 1509 and 1524 nm. Wafer bonding was used to integrate GaAs-AlGaAs distributed Bragg reflectors with an InP-InGaAsP active region.
This paper overviews the properties and possible applications of long wavelength vertical-cavity ... more This paper overviews the properties and possible applications of long wavelength vertical-cavity semiconductor optical amplifiers (VCSOAs). A VCSOA operating in the 1.3-m wavelength region is presented. The device was fabricated using wafer bonding; it was optically pumped and operated in reflection mode. The reflectivity of the VCSOA top mirror was varied in the characterization of the device. Results are presented for 13 and 12 top mirror periods. By reducing the top mirror reflectivity, the amplifier gain, optical bandwidth, and saturation output power were simultaneously improved. For the case of 12 top mirror periods, we demonstrate 13-dB fiber-to-fiber gain, 0.6 nm (100 GHz) optical bandwidth, a saturation output power of 3 5 dBm and a noise figure of 8.3 dB. The switching properties of the VCSOA are also briefly investigated. By modulating the pump laser, we have obtained a 46-dB extinction ratio in the output power, with the maximum output power corresponding to 7-dB fiber-to-fiber gain. All results are for continuous wave operation at room temperature.
IEEE Journal of Selected Topics in Quantum Electronics, 2004
eScholarship provides open access, scholarly publishing services to the University of California ... more eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.
In this work, a novel traveling-wave electroabsorption modulator (TWEAM) by double undercut-etchi... more In this work, a novel traveling-wave electroabsorption modulator (TWEAM) by double undercut-etching i-layers are proposed and successfully fabricated with high-efficiency and high-speed performance
eScholarship provides open access, scholarly publishing services to the University of California ... more eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.
Ultra-high-speed photodetectors and printed-circuit antennas construct photonic transmitters. In ... more Ultra-high-speed photodetectors and printed-circuit antennas construct photonic transmitters. In this letter, we demonstrate a terahertz ͑THz͒ photonic transmitter: edge-coupled membrane photonic transmitters based on metal-semiconductor-metal traveling-wave photodetectors, which are fabricated with low-temperature-grown GaAs photoabsorption layers. With a membrane-based and edge-coupled structure, the demonstrated photonic transmitters can eliminate the requirement of Si lenses and attain an over 20 times higher optical-to-THz power conversion efficiency 2ϫ10 Ϫ4 than vertical illuminated photonic transmitters with Si lenses at the same operation frequency.
2020 Opto-Electronics and Communications Conference (OECC), 2020
Distributed feedback (DFB) lasers are popular light source in high-speed optical access networks;... more Distributed feedback (DFB) lasers are popular light source in high-speed optical access networks; however, the production yield is generally low due to threshold degeneracy from uniform gratings. In this work a holographic-defined two-layer moiré grating structure is utilized to provide a quarter-wavelength phase shift in DFB lasers. In experiments, 200-μm-long DFB lasers exhibit excellent single-wavelength operating behavior (SMSR > 42 dB) in terms of Bragg wavelength, high-speed modulation capability (f3dB = 22 GHz), and high device yield of 86% from 320 laser dies.
2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2017
Nonlinear wavelength generations by using the optical waveguides are more compact, low cost, and ... more Nonlinear wavelength generations by using the optical waveguides are more compact, low cost, and efficient than using the traditional solid state systems [1], and the generated broadband light sources can be utilized in optical coherence tomography, frequency metrology, optical communications, and many other. In this work, the high quality of tantalum pentoxide (Ta<inf>2</inf>O<inf>5</inf>) micro-ring resonator has been fabricated to realize the low power parametric frequency conversion in the communication region. Figure 1 shows the illustration and scanning electron microscope (SEM) image of Ta<inf>2</inf>O<inf>5</inf> based micro-ring resonator. The width/height of the ring waveguides is set as 1.5μm/0.7μm for the anomalous dispersion, which is a key element to minimize the phase mismatch in the parametric frequency conversion process. By fitting the transmission spectrum of the Ta2O5 ring resonator, the load quality factor is ∼5000...
In this study, we propose and demonstrate the enhancement of impurity-free vacancy diffusion (IFV... more In this study, we propose and demonstrate the enhancement of impurity-free vacancy diffusion (IFVD) quantum well intermixing (QWI) using supercritical fluid (SCF) treatment for photonic integration. Using an InGaAsP-based multiple quantum well (MQW) template for local bandgap engineering, SCF CO 2 with H 2 O 2 on a patterned SiO x capping layer could lower the QWI temperature to get a constant wavelength blueshift. Higher oxygen concentration was found in SiO x through high diffusivities and pressures of SCF and dehydration, enabling highly activated Ga 2 O 3 reactions for more vacancies. Additionally, different schemes of semiconductor optical amplifier (SOA)-integrated electroabsorption modulators (EAM) were fabricated. SCF treatment could realize a 9-and 6-dB improvement in extinction ratio and gain, respectively, and then high-speed 45Gb/s modulation, greatly reducing the common issue of p-type dopant (zinc) diffusion during QWI.
A new quantum well, namely InGaAsP/InAlGaAs, is used for electroabsorption modulator. High band-o... more A new quantum well, namely InGaAsP/InAlGaAs, is used for electroabsorption modulator. High band-offset ratio between well and barrier induces strong exciton effect, leading to low fiber-to-fiber loss of -8dB, >25dB extinction ratio, and >30GHz bandwidth.
CLEO/Pacific Rim 2003. The 5th Pacific Rim Conference on Lasers and Electro-Optics (IEEE Cat. No.03TH8671), 2003
We proposed a novel waveguide structure for electroabsorption modulator. By selective undercut et... more We proposed a novel waveguide structure for electroabsorption modulator. By selective undercut etching the active region, the doped conducting layers can be separated. The calculation shows that it has the properties of lower microwave loss, higher microwave speed and higher optical coupling efficiency compared with conventional ridge type.
A low-loss and high-Q Ta 2 O 5 based micro-ring resonator is presented. The micro-ring resonator ... more A low-loss and high-Q Ta 2 O 5 based micro-ring resonator is presented. The micro-ring resonator and channel waveguide with core area of the 700 by 400 nm 2 were fabricated on amorphous Ta 2 O 5 thin films prepared by reactive sputtering at 300°C and post annealing at 650°C for 3 hours. The Ta 2 O 5 micro-ring resonator with a diameter of 200 μm was coupled to the channel waveguide with a coupled Q up to 38,000 at a 0.9 μm coupling gap. By fitting the transmission spectrum of the resonator, the extracted loss coefficient inside the ring cavity and transmission coefficient of TE mode were 8.1dB/cm and 0.9923, leading to the estimated unloaded Q of higher than 44,000. In addition, based on the cutback method, the propagation loss and the coupling loss of Ta 2 O 5 channel waveguide with an inverse taper were 1.5dB/cm and 3.2 dB, respectively. The proposed Ta 2 O 5 technology offers an unique alternative for fabricating high performance guided wave devices, and may well lead to novel applications in photonic integrated circuits.
A degenerate four-wave-mixing (FWM) operation in the Ta<sub>2</sub>O<sub>5</... more A degenerate four-wave-mixing (FWM) operation in the Ta<sub>2</sub>O<sub>5</sub> submicrometer channel waveguide has been successfully demonstrated. The propagation loss of 1.5 dB/cm and total insertion loss of 5.1 dB are realized in a 12.6 mm long waveguide with inverse taper structure. The wavelength and quadratic pumping power-dependent measurements on optical transmission confirm FWM performance and characterize the nonlinearity of waveguide. The conversion efficiency of -50 dB at coupled pump power of 40 mW is observed, suggesting that the nonlinear refractive index of Ta<sub>2</sub>O<sub>5</sub> waveguide at 1550 nm is estimated to be 1×10<sup>-14</sup> cm<sup>2</sup>/W. Our primary results indicate that the…
Using a single cascaded EAM, we demonstrate 13.5-Gbps IM/DD-OFDM transmission over 0~200-km witho... more Using a single cascaded EAM, we demonstrate 13.5-Gbps IM/DD-OFDM transmission over 0~200-km without distance-dependent bit-loading. Dispersion-induced fading and nonlinear distortion in conventional IM/DD systems are settled by novel single-sideband modulation and SSII cancellation schemes, respectively.
A novel scheme of all-optical pattern free 2R regeneration is demonstrated through monolithically... more A novel scheme of all-optical pattern free 2R regeneration is demonstrated through monolithically integration of EAM and SOA. In comparison to Back-to-back case, a clearer 40 Gb/s eye-diagram with 2 dB improvement is obtained.
ABSTRACTWe have developed thin film heaters/sensors that can be integrated on top of superlattice... more ABSTRACTWe have developed thin film heaters/sensors that can be integrated on top of superlattice microcoolers to measure the Seebeck coefficient perpendicular to the layer. In this paper, we discuss the Seebeck coefficients of InGaAs/InAlAs superlattices grown with Molecular Beam Epitaxy (MBE) that have different doping concentrations, varying between 2e18, 4e18, and 8e18 to 3e19 cm−3. It was interesting to find out that – contrary to the behavior in bulk material – the Seebeck coefficient did not decrease monotonically with doping concentration. A preliminary theory of thermoelectric transport in superlattices in the regime of miniband formation has been developed to fit the experimental results. The miniband formation could enhance the thermoelectric power factor (Seebeck coefficient square times electrical conductivity) and thereby improve the Figure of merit, ZT. With this improvement, InGaAs/InAlAs superlattice microcooler become a promising candidate for on-chip temperature c...
2020 IEEE 15th International Conference on Solid-State & Integrated Circuit Technology (ICSICT)
This investigation demonstrates a high-accuracy bidirectional high-voltage (HV) current sensor fa... more This investigation demonstrates a high-accuracy bidirectional high-voltage (HV) current sensor fabricated by CMOS technology. Besides Noise filter, Sense stage, and Controller, the proposed current sensor is featured with a Switching Network composed of transmission gates, which is able to steer the direction of the current. A digital feedback loop comprises Controller generating a pair of digital signals to Switching Network such that the direction of the current is detected real time. The area of the proposed sensor on silicon is 1173x664 um 2 using 0.5 um high-voltage CMOS process, which is very compact to be easily integrated in any portable devices demanding a current monitoring function. The sensing voltage error is 0.7 % by the physical measurements, where the input voltage range is 8~14 V, and the current sensing range is-3~3 A.
An optical modulation scheme by saturating SOA-integrated EAM is used for enhancing high-speed op... more An optical modulation scheme by saturating SOA-integrated EAM is used for enhancing high-speed optical waveform. The saturation conditions on devices will have complemental carrier dynamics, thus leading to significant improvement of extinction ratio and also signal-to-noise ratio.
A negative frequency chirp- and amplitude- compensation in long-distance optical fiber transmissi... more A negative frequency chirp- and amplitude- compensation in long-distance optical fiber transmission by using SOA-integrated EAM have been demonstrated. Data transmission of 36Gb/s 16-QAM OFDM signal with 10.5GHz bandwidth over a 100km single mode fiber.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2009
In multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, the m... more In multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, the multipath components whose delays exceed cyclic prefix (CP) cause inter-symbol interference (ISI) and inter-carrier interference (ICI), which may degrade system performance severely. In this paper, we propose a joint channel estimation and ISI/ICI cancellation scheme in which a limited CP is used in a trade-off against high-rate performance in MIMO-OFDM systems. A channel estimation scheme based on the criterion of Expectation-Maximization (EM) algorithm can be proposed through the use of a training symbol. The EM algorithm uses an iterative procedure to estimate channel parameters and can estimate channel impulse response (CIR) accurately enough to mitigate ISI/ICI influences. Through the accurate CIR estimation, an efficient method has been developed to counteract ISI/ICI influences in signal detection in the case where the inserted CP length is less than the CIR length. Simulation results show that the proposed method can significantly enhance the overall MIMO-OFDM system performance after only a few iterations.
IEEE Journal of Selected Topics in Quantum Electronics, 2001
We report on the fabrication and operation of the first electrically pumped 1.55-m vertical-cavit... more We report on the fabrication and operation of the first electrically pumped 1.55-m vertical-cavity laser array for wavelength-division-multiplexing applications. The array consisted of four channels operating between 1509 and 1524 nm. Wafer bonding was used to integrate GaAs-AlGaAs distributed Bragg reflectors with an InP-InGaAsP active region.
This paper overviews the properties and possible applications of long wavelength vertical-cavity ... more This paper overviews the properties and possible applications of long wavelength vertical-cavity semiconductor optical amplifiers (VCSOAs). A VCSOA operating in the 1.3-m wavelength region is presented. The device was fabricated using wafer bonding; it was optically pumped and operated in reflection mode. The reflectivity of the VCSOA top mirror was varied in the characterization of the device. Results are presented for 13 and 12 top mirror periods. By reducing the top mirror reflectivity, the amplifier gain, optical bandwidth, and saturation output power were simultaneously improved. For the case of 12 top mirror periods, we demonstrate 13-dB fiber-to-fiber gain, 0.6 nm (100 GHz) optical bandwidth, a saturation output power of 3 5 dBm and a noise figure of 8.3 dB. The switching properties of the VCSOA are also briefly investigated. By modulating the pump laser, we have obtained a 46-dB extinction ratio in the output power, with the maximum output power corresponding to 7-dB fiber-to-fiber gain. All results are for continuous wave operation at room temperature.
IEEE Journal of Selected Topics in Quantum Electronics, 2004
eScholarship provides open access, scholarly publishing services to the University of California ... more eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.
In this work, a novel traveling-wave electroabsorption modulator (TWEAM) by double undercut-etchi... more In this work, a novel traveling-wave electroabsorption modulator (TWEAM) by double undercut-etching i-layers are proposed and successfully fabricated with high-efficiency and high-speed performance
eScholarship provides open access, scholarly publishing services to the University of California ... more eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.
Ultra-high-speed photodetectors and printed-circuit antennas construct photonic transmitters. In ... more Ultra-high-speed photodetectors and printed-circuit antennas construct photonic transmitters. In this letter, we demonstrate a terahertz ͑THz͒ photonic transmitter: edge-coupled membrane photonic transmitters based on metal-semiconductor-metal traveling-wave photodetectors, which are fabricated with low-temperature-grown GaAs photoabsorption layers. With a membrane-based and edge-coupled structure, the demonstrated photonic transmitters can eliminate the requirement of Si lenses and attain an over 20 times higher optical-to-THz power conversion efficiency 2ϫ10 Ϫ4 than vertical illuminated photonic transmitters with Si lenses at the same operation frequency.
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Papers by Yi-Jen Chiu