Specific Types of Screen-Based Sedentary Time and Depressive Symptoms in Adolescents

Purpose:Screen-based sedentary behavior(SSB)has been identified as risk factor for mental disorders in most of adolescents.However,there is little literature pertaining to the specific kinds of SSB and its connections with depressive symptoms in most of adolescents.In the present study,we are going tofind out the connections between specific types of SSB and depressive symptoms in Chinese adolescents.Methods:A cross-sectional data based on 996 study participants of middle school students in Guangdong Province.SSB was evaluated by distri-buting the questionnaire of Health Behavior in School-aged Children,while depressive symptoms were evaluated using Chinese version of Children’s Depressive symptoms Inventory(CDI).SSB was categorized into TV/movie time,video games time and other electronic devices-based time(e.g.,mobile phone,computer use).Generalized linear models was used to explore the connections between specific kinds of SSB and depressive symptoms.Results:After controlling for variables of sex,ethnicity,grade,residence,siblings,perceived family affluence,father educational level,mother educational background,body mass index(BMI),physical exercise,duration of sleep,other electronic devices-based time was positively correlated with depressive symptoms in Chinese adolescents(B=0.557%,95%CI:0.187–0.926,p=0.003).This significant connection was also found in girls(B=0.728%,95%CI:0.230–1.225,p=0.004)instead of boys(p>0.05).The other types of SSB were not signifi-cantly in relation to depressive symptoms in adolescents regardless of sex.Conclusion:This study suggested that it might be effective in reducing or preventing depressive symptoms through limiting electronic devices-based time,like computer use or mobile phone use time.This strategy would be particularly useful in girls.Future stu-dies should negate or replicate the research results by introducing more improved study design,which is beneficial to better understand the connections between SSB and depressive symptoms as well as then design more efficient interventions in adolescents.

Widely tunable 2μm optical vortex from a Tm:YAP laser

In this paper,we report on a wide wavelength tuning optical vortex carrying orbital angular momentum(OAM)of±?,from a thulium-doped yttrium aluminum perovskite(YAP)laser employing a birefringent filter.The OAM is experimentally found to be well maintained during the whole wavelength tuning process.The Laguerre-Gaussian(LG_(0,+1))mode with a tuning range of 58 nm from 1934.8 to 1993.0 nm and LG0,-1mode with a range of 76 nm from 1920.4 to 1996.6 nm,are,respectively,obtained.This is,to the best of our knowledge,the first experimental implementation of wavelength tuning for a scalar vortex laser in the 2μm spectral range,as well as the broadest tuning range ever reported from the vortex laser cavity.Such a vortex laser with robust structure and straightforward wavelength tuning capability will be an ideal light source for potential applications in the field of optical communication with one additional degree of freedom.

Large-diameter indium antimonide microwire based broadband and robust optical switch

Various nanophotonic devices based on semiconductor wires with a diameter of several ten nanometers have been studied.Nevertheless,studying the optoelectronics properties and performance of such devices based on large-diameter wires is interesting and meaningful.Here,we successfully grew the micronsized indium antimonide(InSb) wires,and examined their nonlinear optical properties by Z-scan and I-scan(power-dependent) methods within the wavelength range of 0.8-2.8 μm.Furthermore,we demonstrated InSb micro wires(MWs) working as an effective and robust optical switch within 1-2.8 μm wavelength.The findings can open possibilities for research on more large-diameter MWs made from other semiconductor materials for photonic and electronic devices.

Broadband rhenium disulfide optical modulator for solid-state lasers

Rhenium disulfide （ReS2）, a member of group VII transition metal dichalcogenides （TMDs）, has attracted increasing attention because of its unique distorted 1T structure and electronic and optical properties, which are much different from those of group VI TMDs （MoS2, WS2, MoSeg, WSe2, etc.）. It has been proved that bulk ReS2 behaves as a stack of electronically and vibrationally decoupled monulayers, which offers remarkable possibilities to prepare a monolayer ReS2 facilely and offers a novel platform to study photonic properties of TMDs. However, due to the large and layer-independent bandgap, the nonlinear optical properties of ReS2 from the visible to midinfrared spectral range have not yet been investigated. Here, the band structure of ReS2 with the introduction of defects is simulated by the ab initio method, and the results indicate that the bandgap can be reduced from 1.38 to 0.54 eV with the introduction of defects in a suitable range. In the experiment, using a bulk ReS2 with suitable defects as the raw material, a few-layered broadband ReS2 saturable absorber （SA） is prepared by the liquid phase exfoliation method. Using the as-prepared ReS2 SA, passively Q-switched solid-state lasers at wavelengths of 0.64, 1.064, and 1.991 μm are investigated systematically. Moreover, with cavity design, a femtosecond passively modelocked laser at 1.06μm is successfully realized based on the as-prepared ReS2 SA for the first time. The results present a promising alternative for a rare broadband optical modulator and indicate the potential of ReS2 in generating Q-switched and mode-locked pulsed lasers. It is further anticipated that this work may be helpful for the design of 2D optoelectronic devices with variable bandgaps.

Anisotropy of the thermal and laser output properties in Yb,Nd:Sc_(2)SiO_(5) crystal

The anisotropy of thermal property in an Yb,Nd∶Sc_(2)SiO_(5) crystal is investigated from the temperature of 293 to 573 K. Based on the systematical study of thermal expansion, thermal diffusivity, and specific heat, the thermal conductivity in Yb,Nd∶Sc_(2)SiO_(5) crystals orientated at(100),(010),(001), and(406) is calculated to be 3.46, 2.60, 3.35, and 3.68 W=/(m·K),respectively. The laser output anisotropy of a continuous-wave(CW) and tunable laser is characterized, accordingly. A maximum output power of 6.09 W is achieved in the Yb,Nd∶Sc_(2)SiO_(5) crystal with(010) direction, corresponding to a slope efficiency of 48.56%. The tuning wavelength range in the Yb,Nd∶Sc_(2)SiO_(5) crystal orientated at(100),(010), and(001) is 68, 67,and 65 nm, separately. The effects of thermal properties on CW laser performance are discussed.

High peak power 1.0 μm and tri-wavelength 1.3 μm Nd:ScYSiO5 crystal lasers

With a Nd:ScYSiO5 crystal, a high peak power electro-optically Q-switched 1.0 μm laser and tri-wavelength laser operations at the 1.3 μm band are both investigated. With a rubidium titanyle phosphate(RTP) electro-optical switcher and a polarization beam splitter, a high signal-to-noise ratio 1.0 μm laser is obtained, generating a shortest pulse width of 30 ns, a highest pulse energy of 0.765 mJ, and a maximum peak power of 25.5 kW,respectively. The laser mode at the highest laser energy level is the TEM200 mode with the Mvalue in the X and Y directions to be Mx2= 1.52 and My2= 1.54. A tri-wavelength Nd:ScYSiO5 crystal laser at 1.3 μm is also investigated. A maximum tri-wavelength output power is 1.03 W under the absorbed pump power of7 W, corresponding to a slope efficiency of 14.8%. The properties of the output wavelength are fully studied under different absorbed pump power.