High-beam-quality low-resistance vertical-cavity surface-emitting laser array with graphene electrode.

Thermal crosstalk and current crowding effects are pressing issues that significantly impact the beam quality and efficiency of vertical-cavity surface-emitting laser (VCSEL) arrays. In this paper, by taking advantage of the excellent current transmission characteristics of graphene, what we believe to be a novel VCSEL array based on graphene electrode is designed to realize vertical current injections. The series resistance and self-heating of arrays are reduced by controlling the transport direction of the current, effectively suppressing the thermal crosstalk effect. Furthermore, high array beam quality is obtained by optimizing the current density distribution in active regions. Ultimately, the high-power quasi-single mode emission of VCSEL arrays is achieved by introducing graphene electrodes (Gr-VCSEL array) designs. Compared to traditional VCSEL arrays, the 10 × 10 Gr-VCSEL array demonstrates a 41% reduction in series resistance, a side mode suppression ratio of 32 dB, and a divergence angle around 12 °. This structure simultaneously achieves quasi-single mode emission and effectively suppresses the thermal crosstalk effect, providing a new method for the development of high-beam quality VCSEL arrays.

[Cardiovascular effect of positive pressure breathing using G-suits with different bladder coverage].

OBJECTIVE: To compare cardiovascular function of subjects exposed to positive pressure breathing (PPB) while wearing G-suits with different bladder coverage. METHOD: 6 male healthy subjects (18-20 years) wearing three kinds of G-suit with bladder coverage of 45%, 65% and 90% respectively, were exposed to PPB with counterpressures of 30, 50 or 70 mmHg for up to 3 min continuously. G-suit bladder pressure value was three times as high as that of PPB counterpressure. Cardiovascular function was observed every minute. The interval between PPBs was 10 min. The equipment consists of G-suit, jerkin, helmet and mask. RESULT: All subjects completed the experiment successfully. Mean arterial pressure (MAP) elevated significantly, while stroke volume had no striking change, as compared with control group when wearing G-suit with 65% or 90% bladder coverage G-suit. During PPB for 3 min, cardiovascular function didn't change significantly. The mean value of MAP was proportional to the level of PPB. CONCLUSION: The greater G-suit bladder coverage, the less cardiovascular function effect when PPB was conducted simultaneously.

[Cardiovascular responses to G-suits with 3 levels of positive pressure breathing using different chest counter pressures].

OBJECTIVE: To observe cardiovascular responses to positive pressure breathing (PPB) using different counter pressures. METHOD: Cardiovascular responses of 7 male healthy subjects (aged 18-20 years) wearing two kinds of Jerkin-G-suit were observed under three levels of ground-level PPB (30, 50, 70 mmHg) for 3 min. RESULT: All subjects completed the experiment successfully. While during PPB at 50, 70 mmHg levels within 3 min, HR, MAP, TPR elevated significantly, while SV declined significantly. At all 3 PPB levels Q-Z time was not significantly changed. There were significant difference (P<0.05) between delta SV and delta TPR with the two Jerkin-G-suits under PPB of 70 mmHg. CONCLUSION: PPB resulted in elevation of MAP, TPR, HR and decline of SV significantly using two kinds of Jerkin-G-suit. PPB had no effect on contractile function of cardiac muscle. Under PPB, SV increased significantly when chest counter pressure was equal to the mask pressure.