Novel wearable VCSEL-based blood perfusion sensor

A wearable 850 nm VCSEL-based blood perfusion sensor operating on the principles of laser Doppler flowmetry (LDF) and Dynamic Light Scattering (DLS) has been developed and tested. The sensitivity of the sensor to changes in skin blood perfusion has been demonstrated

Discrimination of healthy and cancer cells of the bladder by metabolic state, based on autofluorescence

Bladder cancer is among the most common cancers worldwide (4th in men). It is responsible for high patient morbidity and displays rapid recurrence and progression. Lack of sensitivity of gold standard techniques (white light cystoscopy, voided urine cytology) means many early treatable cases are missed. The result is a large number of advanced cases of bladder cancer which require extensive treatment and monitoring. For this reason, bladder cancer is the single most expensive cancer to treat on a per patient basis. In recent years, autofluorescence spectroscopy has begun to shed light into disease research. Of particular interest in cancer research are the fluorescent metabolic cofactors NADH and FAD. Early in tumour development, cancer cells often undergo a metabolic shift (the Warburg effect) resulting in increased NADH. The ratio of NADH to FAD ("redox ratio") can therefore be used as an indicator of the metabolic status of cells. Redox ratio measurements have been used to differentiate between healthy and cancer breast cells and to monitor cellular responses to therapies. Here, we have demonstrated, using healthy and bladder cancer cell lines, a statistically significant difference in the redox ratio of bladder cancer cells, indicative of a metabolic shift. To do this we customised a standard flow cytometer to excite and record fluorescence specifically from NADH and FAD, along with a method for automatically calculating the redox ratio of individual cells within large populations. These results could inform the design of novel probes and screening systems for the early detection of bladder cancer

517 nm - 538 nm tunable second harmonic generation in a diode-pumped PPKTP waveguide crystal

Tunable continuous wave (CW) green light generation between 517 nm and 538 nm at room-temperature has been demonstrated from a frequency-doubled broadly tunable quantum well (QW) external-cavity fiber-coupled diode laser by use of an uncoated periodically poled potassium titanyl phosphate (PPKTP) crystal aveguide crystal. Green light at 530 nm with maximum conversion efficiency of 14.8% and output power of 12.88 mW has been generated using a PPKTP crystal waveguide with the cross-sectional area of 3x5μm2. The possibility of tunable second harmonic generation in the PPKTP crystal waveguides with the cross-sectional areas of 4x4μm2 and 2x6μm2 was also investigated

A novel type of quasi-phasematching for the second harmonic generation

We propose a novel type of quasi-phasematching for the second harmonic generation in periodically-poled nonlinear crystals. In contrast to the conventional quasiphasematching where one (or few) quasi-wavevector(s) of periodical poling compensate for the momentum mismatch between a pair of the fundamental photons and the SHG one, with the proposed mechanism the momentum mismatch between several pairs of fundamental and SHG photons is compensated with one quasi-wavevector of periodical poling

Quantum-dot saturable absorber and Kerr-lens mode-locked Yb:KGW laser with >450 kW of peak power

The hybrid action of quantum-dot saturable absorber and Kerr-lens mode locking in a diode-pumped Yb:KGW laser was demonstrated. Using a quantum-dot saturable absorber with a 0.7% (0.5%) modulation depth, the mode-locked laser delivered 90 fs (93 fs) pulses with 3.2 W (2.9 W) of average power at the repetition rate of 77 MHz, corresponding to 462 kW (406 kW) of peak power and 41 nJ (38 nJ) of pulse energy. To the best of our knowledge, this represents the highest average and peak powers generated to date from quantum-dot saturable absorber-based mode-locked lasers

Second harmonic generation in a low-loss orientation-patterned GaAs waveguide

The technology of low-loss orientation-patterned gallium arsenide (OP-GaAs) waveguided crystals was developed and realized by reduction of diffraction scattering on the waveguide pattern. The propagation losses in the OP-GaAs waveguide were estimated to be as low as 2.1 dB/cm, thus demonstrating the efficient second harmonic generation at 1621 nm under an external pumping

Femtosecond Alexandrite Laser with InP/InGaP Quantum-Dot Saturable Absorber

A semiconductor saturable absorber mirror (SESAM) passively mode-locked Alexandrite laser was demonstrated. Using an InP/InGaP quantum-dot saturable absorber mirror, pulse duration of 380 fs at 775 nm was obtained. The laser was pumped at 532 nm and generated 295 mW of average output power in mode-locked regime with a pump power of 7.3 W. To the best of our knowledge, this is the first report of a passively mode-locked Alexandrite laser using SESAM in general and quantum-dot SESAM in particular

Femtosecond Alexandrite Laser with InP/InGaP Quantum-Dot Saturable Absorber

A semiconductor saturable absorber mirror (SESAM) passively mode-locked Alexandrite laser was demonstrated. Using an InP/InGaP quantum-dot saturable absorber mirror, pulse duration of 380 fs at 775 nm was obtained. The laser was pumped at 532 nm and generated 295 mW of average output power in mode-locked regime with a pump power of 7.3 W. To the best of our knowledge, this is the first report of a passively mode-locked Alexandrite laser using SESAM in general and quantum-dot SESAM in particular

Near-transform-limited picosecond pulses from a gain-switched InGaAs diode laser with fiber Bragg gratings

We have generated near-transform-limited picosecond pulses(ΔτΔν≈0.45) from a gain-switched diode laser using periodic and chirped fiber Bragg gratings. This configuration reduced the spectral bandwidth from 11 to 0.08 nm and the pulse duration was reduced, from 30 to<18 ps. Average and peak powers of 27 and 770 mW, respectively, were obtained

Second Harmonic Generation with a Fractional Order of Periodical Poling

We demonstrate second harmonic generation in a diode-pumped periodically-poled lithium niobate crystal with a fractional poling period