Direct detection of the transient superresolution effect of nonlinear saturation absorption thin films

Using a strong nonlinear saturation absorption effect is one technique for breaking through the diffraction limit. In this technique, formation of a dynamic and reversible optical pinhole channel and transient superresolution is critical. In this work, a pump–probe transient detection and observation–experimental setup is constructed to explore the formation process directly. A Ge2Sb2Te5 thin film with strong nonlinear saturation absorption is investigated. The dynamic evolution of the optical pinhole channel is detected and imaged, and the transient superresolution spot is directly captured experimentally. Results verify that the superresolution effect originates from the generation of an optical pinhole channel and that the formation of the optical pinhole channel is dynamic and reversible. A good method is provided for direct detection and observation of the transient process of the superresolution effect of nonlinear thin films.

Study on read-only optical disk with Sb mask super-resolution

In this note, by using Sb to replace the Al reflective layer in the conventional optical disk, the recording pits with a diameter 380 nm and a depth 50 nm are read out in the device, whose laser wavelength λ is 632.8 nm and numerical aperture (NA) is 0.40. In the course of reproduction, the readout laser power is 4 mW and the rotation velocity of the disk is 5m/s. The optimum Sb film thickness is 28-30 nm and the CNR is 38-40 dB.

7 kHz sub-nanosecond microchip laser amplified by a grazing incidence double pass slab amplifier

To obtain short pulse width and high peak power laser, a 7 kHz sub-nanosecond microchip laser amplified by a grazing incidence double pass slab amplifier is experimentally demonstrated in this Letter. We use a compact side-pumped Nd∶YVO4 bounce amplifier with grazing incidence beam for achieving high gains and power extraction. Laser output power of 7.37 W at 7 kHz, 1.2 MW pulse peak power with 877 ps duration and 1.05 mJ energy, 25 pm spectral width, and near diffraction limited mode beam quality are achieved, and the optical-to-optical efficiency is 18%. The laser is packaged in a volume of 356 mm × 226 mm × 84 mm and may be used for applications such as laser altimeters and ladar systems.

Image lithography in telluride suboxide thin film through controlling “virtual” bandgap

In this work, TeO_(0.7)thin films were prepared by the reactive magnetron-controlling sputtering method. Complex gray-scale patterns were successfully fabricated on TeO_(0.7)thin films through the laser direct writing method.The structural origin of TeO_(0.7)thin film was investigated for gray-scale pattern formation. It is found that multiple gray-scale levels are dependent on the "virtual" bandgap energy of TeO_(0.7)thin films. The bandgap energy changes lead to refractive index and reflectivity difference. Thus, gray-scale tones can be formed. By accurately controlling laser energy, various "virtual" bandgaps can be generated in TeO_(0.7)thin films, and colorful gray-scale levels can be formed. Experimental results indicate that TeO_(0.7)thin film can be used as micro/nano image writing material.

False nonlinear effect in z-scan measurement based on semiconductor laser devices:theory and experiments

With the development of semiconductor technology,semiconductor laser devices and semiconductor laser pump solid-state laser devices have been widely applied in z-scan experiments.However,the feedback light-induced output instability of semiconductor laser devices can negatively affect the accurate testing of the nonlinear index.In this work,the influence of feedback light on z-scan measurement is analyzed.Then the calculated formula of feedback light-induced false nonlinear z-scan curves is theoretically derived and experimentally verified.Two methods are proposed to reduce or eliminate the feedback light-induced false nonlinear effect.One is the addition of an attenuator to the z-scan optical path,and the other is the addition of an opto-isolator unit to the z-scan setup.The experimental and theoretical results indicate that the feedback light-induced false nonlinear effect is markedly reduced and can even be ignored if appropriate parameters are chosen.Thus,theoretical and experimental methods of eliminating the negative effect of feedback light on z-scan measurement are useful for accurately obtaining the nonlinear index of a sample.