Publications by authors named "Yung Fu Chen"

For accurate measurement of carboxyhemoglobin level in the blood, a compact dual-wavelength laser at 555 and 579.5 nm with conversion efficiency up to 27.5% is originally developed by using Nd:YVO/KGW/LBO laser with intracavity stimulated Raman scattering (SRS), second harmonic generation (SHG), and sum frequency generation (SFG).

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We develop a compact high-frequency actively Q-switched Nd:YVO/YVO Raman laser at 1525 nm. The mode size stability and the mode overlapping are numerically analyzed to craft the resonator. Experimental results reveal that the compact cavity and the cavity dumping effect lead to the considerable narrowing of the pulse width.

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High-power efficient continuous-wave Nd:YVO/KGW Raman lasers at 555 and 559 nm are achieved by using a double-sided dichroic coating output coupler to improve the resonance quality factor. The Np-cut potassium gadolinium tungstate (KGW) is used to generate the Stokes waves at 1159 and 1177 nm by placing the polarization of the1064 nm fundamental wave parallel to the Ng and Nm axes, respectively. The lithium triborate (LBO) crystal with the cut angle in the XY plane for the type-I phase matching is used to perform the intracavity sum frequency generation for yielding the green light at 555 nm and the lime light at 559 nm at the optimal phase matching temperature.

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Compact efficient high-power continuous-wave Nd:YVO Raman lasers for selectable wavelengths within 559-603 nm are achieved by using KGW crystal for intracavity stimulated Raman scattering (SRS) and lithium triborate (LBO) crystal for intracavity sum frequency generation (SFG) and second harmonic generation (SHG). The LBO crystal with the cut angle in the XY plane for the type-I phase matching is used to perform intracavity SHG or SFG. Experimental results reveal that the participated Stokes lines include the internal vibration mode at 901 cm, the external vibrational mode at 209 cm, and the combination mode of the 901 cm and 209 cm Raman shifts.

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Two compact laser sources at 707 and 714 nm are realized efficiently by using a diode-pumped a-cut Nd:YVO laser with intracavity stimulated Raman scattering and sum-frequency generation (SFG). The fundamental wave at 1342 nm is generated by the F → I transition in Nd:YVO crystal. The Raman Stokes waves at 1496 and 1526 nm were obtained by placing the c-axis of the Nd:YVO crystal along the Ng and Nm axes of an Np-cut KGW crystal, respectively.

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A compact efficient continuous wave (CW) laser with selectable two wavelengths at 671 and 714 nm is developed. The laser cavity comprises an Nd-doped and an undoped YVO crystal to generate the fundamental wave at 1342 nm and the first-Stokes Raman wave at 1525 nm, respectively. A single LBO crystal with the cut angle in the XZ plane is designed to achieve the selectable phase-matching via the thermal tuning for the second harmonic generation (SHG) of 1342 nm and the sum frequency generation (SFG) of 1342 and 1525 nm.

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Article Synopsis
  • * A unique Np-cut KGW crystal is used to selectively produce either a yellow 579 nm laser or an orange 589 nm laser, enhancing versatility.
  • * The design features a compact resonator that boosts efficiency, with the orange laser achieving output energies up to 0.08 mJ and peak powers of 50 kW, while the yellow laser can reach 0.10 mJ and 80 kW peak power.
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Heterogeneous integration of monolayers is an emergent route of spatially combining materials with available platforms for unprecedented properties. A long-standing challenge along this route is to manipulate interfacial configurations of each unit in stacking architecture. A monolayer of transition metal dichalcogenides (TMDs) offers an embodiment of studying interface engineering of integrated systems because optoelectronic performances generally trade off with each other due to interfacial trap states.

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  • * A new system was developed to automatically detect LVH from ECG signals by extracting specific features from R-peak and S-valley amplitudes using a back propagation neural network (BPN).
  • * The BPN model demonstrated high accuracy and performance in detecting LVH, surpassing existing ECG criteria and previous artificial intelligence models.
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  • - The Taiwan Axion Search Experiment with a Haloscope focused on detecting axions by utilizing a microwave cavity in the frequency range of 4.70750 to 4.79815 GHz.
  • - The experiment did not find any significant axion signals, with the highest significance being 3.355, but it was able to exclude certain theoretical models of axion interactions.
  • - This study achieved unprecedented sensitivity, improving constraints on axion-two-photon coupling in the mass range of 19.4687 to 19.7639 μeV, surpassing previous nonhaloscope experiments by three orders of magnitude.
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We report on a holoscope axion search experiment near 19.6 µeV from the Taiwan Axion Search Experiment with Haloscope collaboration. This experiment is carried out via a frequency-tunable cavity detector with a volume V = 0.

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The resonant modes generated from the modern Chladni experiment are systematically confirmed to intimately correspond to the maximum entropy states obtained from the inhomogeneous Helmholtz equation for the square and equilateral triangle plates. To investigate the origin of maximum entropy states, the inhomogeneous Helmholtz equation is modified to consider the point interaction coming from the driving oscillator. The coupling strength associated with the point interaction is characterized by a dimensionless factor .

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Electric circuits influenced by thermal noise are analogous to confined Brownian particles and can be an alternative and convenient scheme for studying stochastic thermodynamics. Here we experimentally demonstrate an effective technique of generating tunable potentials for Brownian dynamics in an electric circuit, realized by external controlled feedback. We present two illustrative examples of one-dimensional virtual potentials: static harmonic potential and time-varying double-well potential.

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We study the nonequilibrium steady-state (NESS) dynamics of two-dimensional Brownian gyrators under harmonic and nonharmonic potentials via computer simulations and analyses based on the Fokker-Planck equation, while our nonharmonic cases feature a double-well potential and an isotropic quartic potential. In particular, we report two simple methods that can help understand gyrating patterns. For harmonic potentials, we use the Fokker-Planck equation to survey the NESS dynamical characteristics; i.

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Article Synopsis
  • Nanoelectronics using two-dimensional (2D) materials face challenges due to contact issues with semiconducting monolayers, particularly in creating p-type transistors with low Schottky barriers.
  • Tungsten selenides (WSe) have shown promise for p-type transistors but require high growth temperatures, which can lead to inconsistencies.
  • This study demonstrates a method to grow WSe at a reduced temperature of 800°C using a seeding promoter and low-pressure chemical vapor deposition, resulting in high-quality interfaces with graphene, characterized by transmission electron microscopy (TEM).
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An efficient LED pumping module is explored for the demonstration of energy scaling of passively Q-switched output to millijoule high-pulse-energy level. For the free-running operation at fundamental wavelength, the highest optical conversion efficiency of 23.7% is reached.

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We demonstrate the direct generation of visible vortex beams at 640 nm and 607 nm by employing an off-axis pumping scheme in a diode end-pumped Pr:YLF laser. A detailed numerical analysis, based on the coherent superposition of Hermite-Gaussian modes with different amplitudes and phases, is perfectly consistent with the experimentally observed lasing modes. The maximum vortex output powers have been measured to be 808 mW and 211 mW at a pump power of 3.

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We implement a logic switch by using a graphene acoustoelectric transducer at room temperature. We operate two pairs of inter-digital transducers (IDTs) to launch surface acoustic waves (SAWs) on a LiNbO substrate and utilize graphene as a channel material to sustain acoustoelectric current I induced by SAWs. By cooperatively tuning the input power on the IDTs, we can manipulate the propagation direction of I such that the measured I can be deliberately controlled to be positive, negative, or even zero.

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The design criterion of thermal conductivity for the GaAs/AlAs distributed Bragg reflector (DBR) superlattice structure was thoroughly investigated to precisely analyze the thermal behaviors of the optically pumped vertically external cavity surface-emitting laser (VECSEL). A finite element model with detailed configuration of a VECSEL gain chip was constructed to fulfill the analysis. A 1060 nm VECSEL with different pump conditions was further demonstrated to verify the finite element analysis.

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Article Synopsis
  • A novel mode-locked laser scheme is created using a reflected Fabry-Perot (FP) cavity, resulting in stable continuous-wave operation with a repetition rate of 48 MHz and average output power of 2.6 W.
  • The pulse width of the laser can be adjusted by changing the optical thickness of the FP cavity, ranging from 0.8 to 2.6 ns.
  • The study highlights the importance of the reflected FP cavity in generating optical pulses with narrow spectral linewidths, offering a promising approach for future laser technologies.
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Erectile dysfunction (ED) affects millions of men worldwide. Men with ED generally complain failure to attain or maintain an adequate erection during sexual activity. The prevalence of ED is strongly correlated with age, affecting about 40% of men at age 40 and nearly 70% at age 70.

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Objective: To assess effectiveness of the video-based m-health system providing videos dictated by physicians for health education and symptom self-management for patients with Interstitial cystitis/bladder pain syndrome (IC/BPS).

Methods: An m-health system was designed to provide videos for weekly health education and symptom flare self-management. O'Leary-Sant index and visual analogue scale as well as SF-36 health survey were administrated to evaluate the disease severity and quality of life (QoL), respectively.

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More than 1 billion people suffer from chronic respiratory diseases worldwide, accounting for more than 4 million deaths annually. Inhaled corticosteroid is a popular medication for treating chronic respiratory diseases. Its side effects include decreased bone mineral density and osteoporosis.

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A continuous-wave (cw) self-mode-locked Tm:YAG laser at 2015 nm is successfully demonstrated by suppressing the self-pulsing behavior. By using rate equations to simulate the laser temporal dynamic, the theoretical analysis indicates that the reabsorption-induced self-pulsing for the Tm:YAG laser can be suppressed with sufficient pump power. It is experimentally confirmed that at absorbed powers higher than 6 W, the self-pulsing can be eliminated and a cw self-mode-locked pulse is generated instead of the Q-switched mode locking.

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