International Journal of Optics

GaN multiquantum-well blue light-emitting diodes (LEDs) were radiated with ⁶⁰Co γ-rays for accumulated doses up to 2.5 Mrad (SiO₂). The radiation-induced current and 1/f noise degradations were studied when the devices operate at the low bias voltage. The current increased by 2.31 times, and the 1/f noise increased by 275.69 times after a dose of 2.5 Mrad (SiO₂). Based on Hurkx’s trap-assisted tunneling model, the degradation of current was explained. γ radiation created defects in the space-charge region of LEDs. These defects as generation-recombination centers lead to the increase in the current. In addition, based on the quantum l/f noise theory, the degradation of 1/f noise might be also attributed to these defects, which caused an increase in the Hooge constant and a decrease in the carrier lifetimes. The current and 1/f noise degradations can be attributed to the same physical origin. Compared to the current, the 1/f noise parameter is more sensitive, so it may be used to evaluate the radiation resistance capability of GaN blue LEDs.

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A mode-locked and Q-switched short pulse laser using the Nd³⁺/Cr³⁺:YAG ceramic has been constructed with a SESAM and Cr⁴⁺:YAG crystal optical switch based on excite state absorption (ESA). Laser oscillations of the pulse laser were observed experimentally. The Nd/Cr:YAG ceramic laser has a high conversion efficiency from white light (such as lamp light or solar light) to the laser. The Nd/Cr:YAG ceramic has a higher laser gain than the Nd:YAG laser for the same pumping power. The laser oscillation can be obtained very easily. A single-mode-locked laser pulse with fast modulation on the order of 100 ps was obtained in some pump power regimes when using the Cr⁴⁺:YAG crystal. The obtained pulse duration of the short pulse was a few hundred ps. A maximum peak power of 60 kW was obtained when using a SESAM. The same level of peak power (60 kW) was also obtained when using the Cr⁴⁺:YAG crystal.

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Fiber optic communication systems (FOCSs) have attained a lot of attention by revolutionizing the telecommunication industry and offering new possibilities with the technical advancements in state-of-the-art high speed digital electronics. Advanced modulation formats make use of the phase, amplitude, and polarization of the optical signals at the same time to provide high spectral efficiency as compared with 1 bit/s/Hz for the intensity modulation direct detection system (IMDD), but are highly prone to transmission impairments. Thus, the effects that add up to the optical fiber impairments such as optical fiber chromatic dispersion (OFCD), polarization model dispersion (PMD), and phase offset and noise (POaN) need to be addressed at the receiver side. The development of components and algorithms to minimize these effects in next generation FOCSs with 100 Gbps data rate and beyond with long-haul transmission is still a challenging issue. In this paper, digital signal processing- (DSP-) assisted dispersion and nonlinear compensation techniques are presented to compensate for physical layer impairments including OFCD, PMD, and POaN. The simulations are performed considering Dual Polarization- (DP-) QPSK modulation format to achieve two-fold data rate to achieve spectral efficiency of 3.28 bits/s/Hz by making use of the polarization diversity and system performance is investigated in terms of bit error rate (BER), constellation diagrams, and quality factor (Q-factor) for different values of optical signal-to-noise ratio (OSNR), launch power (), and fiber length.

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Sum squeezing of the field amplitude is studied in the nondegenerate and degenerate frequency upconversion process under the short interaction time. It is shown that sum squeezing can be converted into normal squeezing via sum-frequency generation in the nondegenerate frequency upconversion process, while the amplitude-squared squeezing of the fundamental mode directly changed into the squeezing of the harmonic in the degenerate frequency upconversion process. All reachable conditions of uncorrelated modes for obtaining a sum squeezing in two modes and its dependence on the squeezing of individual field modes are investigated. It is found that the squeezed states are associated with large number of pump photons. It is also confirmed that the higher-order squeezing (sum squeezing) is directly associated with coupling of the field and interaction time.

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Oral surgery mainly provides surgical scope illumination by doctors wearing headlamps, but there are still clinical restrictions on use. The limitations are (1) due to the angle of the head swing and the shadow of the visual field during the operation and (2) due to projection of the light source being worn on the doctor’s head and the length of the wire, and the fiber-optic wire will affect the relative position of the surgical instrument and limit the scope of the doctor’s activity. This study will focus on the development of oral lighting optical microstructure devices to solve and improve the abovementioned clinical use limitations. The production method is to make an oral lighting mold by 3D printing technology and use the polydimethylsiloxane (PDMS) of liquid silicone material to make an oral lighting device with mold casting technology. The results show that the optical simulation achieves the target light distribution by optimizing the three geometric reflection surfaces combined with the lens design by the optimization method, and the maximum illumination value can reach 5102 lux. According to the measurement results of mold casting technology, the average errors of the profile of the 3D printing finished product and the PDMS finished product of the oral device structure are about 1.4% and 16.9%, respectively. Because the contour of the PDMS finished product’s error caused the light to shift by 0.5∼3 mm distance, the light is still concentrated in the range of the tonsils, so this study can be defined as within the acceptable range of within 16.9% of the intra lighting error. The development of oral lighting devices in this study will reduce the burden on physicians in nonprofessional fields, reduce the time of surgery for patients to maintain the health of doctors, and rise the level of medical equipment to increase surgical safety.

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Hyperspectral remote-sensing images have the characteristics of large transmission data and high propagation requirements, so they are faced with transmission and preservation problems in the process of transmission. In view of this situation, this paper proposes a spectral image reconstruction algorithm based on GISMT compressed sensing and interspectral prediction. Firstly, according to the high spectral correlation of hyperspectral remote-sensing images, the hyperspectral images are grouped according to the band, and a standard band is determined in each group. The standard band in each group is weighted by the GISMT compressed sensing method. Then, a prediction model of the general band in each group is established to realize the remote-sensing image reconstruction in the general band. Finally, the difference between the actual measured value and the predicted value is calculated. According to the prediction algorithm, the corresponding difference vector is obtained and the predicted measured value is iteratively updated by the difference vector until the hyperspectral reconstructed image of the relevant general band is finally reconstructed. It is shown by experiments that this method can effectively improve the reconstruction effect of hyperspectral images.

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