Yuanfu Lu

High-efficiency 355 nm generation in barium aluminum borate diflouride (BaAlBO3F2)

We demonstrate high-efficiency ultraviolet (UV) laser generation in a nonlinear optical crystal BaAlBO3F2 (BABF); 355 nm UV light was generated by using a type I BABF crystal as a sum-frequency mixing of the fundamental light and the second harmonic from a picosecond Nd:YAG laser operated at a repetition rate of 10 Hz with a pulse duration of 20 ps. An output of 0.635 mJ for the third harmonic was obtained. The conversion efficiency was 26.4%. As far as we know, it was the first time that third-harmonic generation in BABF was achieved. Obviously, the BABF crystal is a promising UV nonlinear optical material because of its relatively large nonlinear coefficient and nonhygroscopicity.

High average power 1.5 microm eye-safe Raman shifting in BaWO4 crystals.

A nanosecond 1.3 microm Nd:YAG laser-pumped external cavity eye-safe Raman laser based on BaWO(4) crystal is efficiently demonstrated. The average power of 1.5 microm was 0.60 W operating at a pulse repetition rate of 1.7 kHz and an incident pump power of 4.14 W. Conversion efficiency of 14.5% and a high slope efficiency of 54.5% have been achieved. Pulse shortening was obviously observed. The pulse duration of the first Stokes was about 40 ns, much shorter than the fundamental pulse with a duration of approximately 220 ns.

2-\mum singly resonant optical parameter oscillator

We experimentally realize a singly resonant optical parameter oscillator (OPO) which operates at the degenerate point of KTiOPO4 (KTP) crystal. A thin film plate polarizer (TFP) is used as the output coupler to obtain linearly polarized 2.12 \mum laser. A maximum output power of 2.2 W at 2.12 \mum is obtained from a near-degenerate, type-II KTP OPO by utilizing a Q-switched diode-pumped Nd:YAG laser operating at 5 kHz.

The annealing effects on the micro-structure and properties of RuMoC films as seedless barrier for advanced Cu metallization

100 nm thick RuMoC films and 5 nm thick RuMoC films with Cu capping have been deposited on Si(111) by magnetron co-sputtering with Ru and MoC confocal targets. The samples were subsequently annealed at temperatures ranging from 450 to 650 °C in vacuum at a pressure of 3 × 10−4 Pa to study the annealing effects on the microstructures and properties of RuMoC films for advanced seedless Cu metallization applications. The sheet resistances, residual oxygen contents, and microstructures of the RuMoC films have close correlation with the doping contents of Mo and C, which can be easily controlled by the deposition power ratio of MoC versus Ru targets (DPR). When DPR was 0.5, amorphous RuMoC film (marked as RuMoC II) with low sheet resistances and residual oxygen contents was obtained. The fundamental relationship between the annealing temperatures with the microstructures and properties of the RuMoC films was investigated, and a critical temperature point was revealed at about 550 °C where the components and mi...

Spectroscopic measurements and terahertz imaging of the cornea using a rapid scanning terahertz time domain spectrometer

Spectroscopic measurements and terahertz imaging of the cornea are carried out by using a rapid scanning terahertz time domain spectroscopy (THz-TDS) system. A voice coil motor stage based optical delay line (VCM-ODL) is developed to provide a rather simple and robust structure with both the high scanning speed and the large delay length. The developed system is used for THz spectroscopic measurements and imaging of the corneal tissue with different amounts of water content, and the measurement results show the consistence with the reported results, in which the measurement time using VCM-ODL is a factor of 360 shorter than the traditional motorized optical delay line (MDL). With reducing the water content a monotonic decrease of the complex permittivity of the cornea is observed. The two-term Debye relaxation model is employed to explain our experimental results, revealing that the fast relaxation time of a dehydrated cornea is much larger than that of a hydrated cornea and its dielectric behavior can be affected by the presence of the biological macromolecules. These results demonstrate that our THz spectrometer may be a promising candidate for tissue hydration sensing and practical application of THz technology.

An interferometric sensor based on visibility modulation

We propose and demonstrate an interferometric sensor based on visibility modulation. In the interferometric sensor, a section of polarization maintain (PM) fiber is spliced into one arm as the sensing head. Due to the interference between the two beams in the two arms, respectively, an interferometric fringe can be obtained. The birefringence of the PM fiber splits the beam in the sensing arm, yielding a visibility envelop in the interferometric fringe. Strain applied on the PM fiber can be demodulated by measuring the visibility change in a given wavelength. Experimental result shows that the sensor can achieve resolution of up to 28 nano-strain. This demodulation scheme is immunity to the wavelength shift and power fluctuation of OSA, thus improving the accuracy of the sensor. This type of sensor can be improved by using a wavelength-swept laser or a mode-locked fiber laser.

Low cost multi-channels Gallium Arsenide absorption-based fiber optic temperature sensing system

This paper proposed a solution about low cost multi-channels Gallium Arsenide (GaAs) absorption-based fiber optic temperature sensing system, which can get specific channel temperature information at pre-set time slots by combining time division multiplexing technology and fiber optic multiplexing module. Established an seven channels fiber optic temperature sensing system using only one spectrum analysis unit and achieved -/+ 1°C temperature resolution, 2Hz measuring frequency at temperature range from 0°C to 150°C.