Spectral Feature Analysis of Semiconductor Thin Disk Laser

The semiconductor thin disk laser is a new type of semiconductor laser. This work gives the basic operation function of the semiconductor disk laser, and analyses the heat effect by the experimentally measured photoluminescence spectrum of the laser chip at different pump power and different temperatures. We can see that: with increasing pump power, the thermal effect of the gain material becomes seriously and causes the saturation of carrier lifetime, so the electron-hole pair created in the absorbtion layer has no enough time to rate to one of the wells, and the non-radiative recombination happens in the barrier. When the thermal effect becomes stronger, the chip will be not lasing. This phenomenon is from the smaller energy offset between barrier and quantum well. We optimize the original structure design and experimental technology. A non-absorbing AlGaAs layer which is transparent to the pumping and laser wavelength is added to confine the carriers in the quantum wells. At the same time a DBR with double reflecting band is induced to improve the absorbing efficiency of the pumping light. The single QW is replaced by the three narrow QWs. This three QWs structure can add the quantum state of QW, increase the recombination probability of carriers in the QWs and reduce the heat effect. The chemical etching equipment is also improved to control the surface unevenness to be within 50 nm.

Detection of a high-confidence quasi-periodic oscillation in radio light curve of the high redshift FSRQ PKS J0805–0111

In this work,we have searched for quasi-periodic oscillations(QPOs)in the 15 GHz light curve of the FSRQ PKS J0805-0111 monitored by the Owens Valley Radio Observatory(OVRO)40 m telescope during the period from 2008 January 9 to 2019 May 9,using the weighted wavelet Z-transform(WWZ)and the Lomb-Scargle Periodogram(LSP)techniques.This is the first time to search for a periodic radio signal in the FSRQ PKS J0805-0111 by these two methods.Both methods consistently reveal a repeating signal with a periodicity of 3.38±0.8 yr(>99.7%confidence level).In order to determine the significance of the periods,the false alarm probability method was applied,and a large number of Monte Carlo simulations were performed.As possible explanations,we discuss a number of scenarios including the thermal instability of thin disks scenario,the spiral jet scenario and the binary supermassive black hole scenario.We expect that the binary black hole scenario,where the QPO is caused by the precession of binary black holes,is the most likely explanation.FSRQ PKS J0805-0111 thus could be a good binary black hole candidate.In the binary black hole scenario,the distance between the primary black hole and the secondary black hole is about 1.71×10^(16) cm.

Photosensitivity Spectra of Thin Films from a CdSexS1-x Solid Solution

The results of a study of the energy spectra of the activation of intrinsic defects of a photosensitive film made from the CdSexS1-x solid solution depending on the conditions of preparation and heat treatment in various media are presented. It is shown that at x = 0.8 cadmium vacancies create a deep level with an activation energy Еv + (0.63 ± 0.02) eV, a complex of chlorine atom with a cadmium vacancy creates a level Еv + (0.43 ± 0.02) eV, as well as the fast recombination center Еv + (0.92 ± 0.02) eV. The formation of selenium vacancies due to the introduction of chlorine and its combination with cadmium leads to the appearance of a sticking level Еc - (0.19 ± 0.02) eV. CdSe0.8S0.2 films can be used to develop light emitting diodes, photo sensors, IR and visible lasers.

Cellulose-based photocatalytic paper with Ag_(2)O nanoparticles loaded on graphite fibers

TiO_(2) nanoparticle is the most extensively used photocatalyst for photocatalytic paper.However,TiO_(2) nanoparticle is active only under UV light that accounted for less than 5%of the solar light energy.There is a need to develop a photocatalytic paper with full spectrum photoactivity.Herein,a full spectrum photocatalytic paper was fabricated by incorporating cellulose fibers with graphite fibers which were pre-loaded with Ag_(2)O nanoparticles.X-ray diffraction(XRD)testing and scanning electron microscopy(SEM)examination confirmed the loading of the Ag_(2)O nanoparticles onto the graphite fibers.The photocatalytic activity of the paper was evaluated with the degradation of methyl orange(MO)under ultraviolet,visible or near-infrared light irradiation.It was found that the degradation rate of MO could reach 32%,19%and 19%under UV,visible and NIR light,respectively after 3 h of irradiation.Meanwhile,the photocatalytic paper was very stable and can be reused repeatedly.Antibacterial tests showed that the photocatalytic paper could inhibit Escherichia coli(E.coli)growth under office lighting condition.