Band-Reject Filters for Bragg Mirror Using Perturbed Chiral Sculptured Thin Films

We have theoretically simulated the optical properties of perturbed chiral STF （sculptured thin film） with and without defect. It was revealed that such STFs could act as band-reject filters with tunable Bragg regime of free space wavelengths and different bandwidth through changing the vapor incident angle during glancing angle deposition process. These Bragg filters are narrowing due to the change of vapor incident angle for circularly polarized light. Interestingly, as the vapor incident angle increased, the band-rejected filter exhibited to decrease the bandwidth and shifted in the Bragg regime, indicating that such STF nanostructures have high potential for behaving as unique polarization insensitive Bragg mirror.

800nm Semiconductor Absorber with Low Temp erature Method and Surface State Method Combined Absorber for Kerr Lens Modelocking of Ti:Al_2O_3 Laser

A novel 800nm Bragg mirror type of semiconductor saturable absorption mirror wit h low temperature method and surface state method combined absorber is presented .With which passive Kerr lens mode locking of Ti∶Al 2O 3 laser pumped by argo n ion laser is realized,which produces pulses as short as 40fs.The spectrum band width is 56nm,which means that it can support the modelocking of 20fs.The pulse frequency is 97.5MHz;average output power is 300mW at the pump power of 4.45W.

Biological reaction signal enhancement in porous silicon Bragg mirror based on quantum dots fluorescence

In this paper, we mainly study the preparation of an optical biosensor based on porous silicon(PSi) Bragg mirror and its feasibility for biological detection. The quantum dot(QD) labeled biotin was pipetted onto streptavidin functionalized PSi Bragg mirror samples, the affinity reaction between QD labeled biotin and streptavidin in PSi occurred, so the QDs were indirectly connected to the PSi. The fluorescence of QD enhanced the signal of biological reactions in PSi. The performance of the sensor is verified by detecting the fluorescence of the QD in PSi. Due to the fluorescence intensity of the QDs can be enhanced by PSi Bragg mirror, the sensitivity of the PSi optical biosensor will be improved.

Dual-wavelength erbium-doped fiber laser with asymmetric fiber Bragg grating Fabry-Perot cavity

A novel dual-wavelength fiber laser with asymmetric fiber Bragg grating(FBG) Fabry-Perot(FP) cavity is proposed and experimentally demonstrated. A couple of uniform FBGs are used as the cavity mirrors, and the third FBG is used as intracavity wavelength selector by changing its operation temperature. Experimental results show that by adjusting the operation temperature of the intracavity wavelength selector, a tunable dual-wavelength laser emission can be achieved. The results demonstrate the new concept of dual-wavelength lasing with asymmetric FBG FP resonator and its technical feasibility.

Numerical modeling of thermal loading of diamond crystal in X-ray FEL oscillators

Due to high reflectivity and high resolution of X-ray pulses, diamond is one of the most popular Bragg crystals serving as the reflecting mirror and mono-chromator in the next generation of free electron lasers（FELs）.The energy deposition of X-rays will result in thermal heating, and thus lattice expansion of the diamond crystal,which may degrade the performance of X-ray FELs. In this paper, the thermal loading effect of diamond crystal for X-ray FEL oscillators has been systematically studied by combined simulation with Geant4 and ANSYS, and its dependence on the environmental temperature, crystal size, X-ray pulse repetition rate and pulse energy are presented. Our results show that taking the thermal loading effects into account, X-ray FEL oscillators are still robust and promising with an optimized design.