In this paper, based on the rate equations model for injection locked semiconductor ring laser, new equations are developed for modelling the detuning frequency and direct modulation response of the slave laser as well as the amplitude and phase modulation response of the master laser. Results show that by increasing the injection power of the master laser, the dynamic characteristics of the slave laser are improved consequently, locking area range, relaxation oscillation frequency and slave laser direct modulation bandwidth as well as field amplitude and phase of the master laser are enhanced by comparing the result of different modulation schemes. It is observed that master phase modulation configuration provides the largest bandwidth while the output response is considered amplitude of the slave laser (80 times of the slave laser direct modulation frequency response).

In this paper we explain in detail the design of a semiconductor laser coupled with the reflected beams from a grating. Since the beams reflected are diffracted at different angles, only one component of them can be resonated in the cavity. This technique reduces the output frequency of the laser and increases its stability.Since this system has various applications in the spectroscopy, gas concentrations, air pollution measurements, investigation of atomic and molecular structure, and so on, the system is believed to be simple and accurate. This design is made for the first time in Iran and its reliability has been tested by the measurement of the rubidium atom, and the result is given.

Purpose: Photothermal therapy (PTT) is a procedure that converts laser beam energy to heat so can disturb tumor cells. Carbon nanotubes (CNTs) have unique properties in absorption optical energy and could change optical power into heat in PTT procedures. Additionally, titanium dioxide (TiO2) nanoparticles (NPs) have a unique feature in absorbing and scattering light. Therefore, these mentioned NPs could play a synergistic role in the PTT method. Methods: CNTs and TiO2 NPs were injected into the melanoma tumor sites of cancerous mice. Then sites were excited using the laser beam (λ,= 808 nm, P = 2 W, and I = 4 W/cm2). Injected NPs caused hyperthermia in solid tumors. Tumor size assay, statistical analysis, and histopathological study of the treated cases were performed to assess the role of mentioned NPs in PTT of murine melanoma cancer. Results: The results showed that CNTs performed better than TiO2 NPs in destroying murine melanoma cancer cells in animals. Conclusion: The present study compared the photothermal activity of excited CNTs and TiO2 NPs in cancer therapy at the near-infrared spectrum of light. Tumors were destroyed selectively because of their weakened heat resistance versus normal tissue. PTT of malignant melanoma through CNTs caused remarkable necrosis into the tumor tissues versus TiO2 NPs.

Low power consumption, low chip area and fabrication in the standard complementary metal oxide semiconductor (CMOS) process are vital requirements for oscillators used in low-cost bio-implantable and wearable devices. Conventional ring oscillators (ROs) are good candidates for using in biomedical applications. However, their oscillation frequency strongly depends on the temperature. In this study, a temperature compensated ring oscillator with low power consumption is proposed. The transistors of the proposed ring oscillator operate in the subthreshold region to achieve a low power and low voltage performance. Since, in the subthreshold region, the oscillation frequency of a conventional ring oscillator increases with increase in the temperature, two current sources are used to power the proposed subthreshold ring oscillator: a temperature independent current source and a complementary to absolute temperature (CTAT) current source. In the proposed circuit, the CTAT current forms a small part of the total supplied current and its duty is to compensate for the oscillation frequency deviation. Two prototypes of the subthreshold ring oscillator were designed and simulated for a target frequency of 1MHz using commercially available 0.18µm RF-CMOS technology. The thermal coefficient (TC) of the uncompensated ring oscillator was 2400 ppm/ºC from -40ºC to 85ºC, though applying the proposed technique reduces the TC of the ring oscillator to 80.4 ppm/ºC with total power consumption as low as 14.5µW.

In this paper, Langevin rate equations governing the behavior of a single-mode semiconductor laser are solved numerically and various noise characteristics are calculated from the results of numerical solution. Using the stochastic dynamic equations of field and population inversion, including nonlinear gain, we obtain intensity autocorrelation function, intensity noise versus injection current characteristic, intensity and frequency noise spectra, lineshape, and linewidth of laser.

Transfer matrix method (TMM) has been applied to analyze characteristics of semiconductor laser optical amplifiers. The input signal is sinusoidal modulating wave and we do not assume the modulating bias signal as well. We have shown that the distortion arises from gain modulation at low modulation frequencies, but in microwave modulation frequencies, the gain takes an average value and the response becomes linear.

In this paper, a precise method for computing the optical gain/loss in an optically pumped semiconductor material is reported. Variations of the gain coefficient, as a function of pump light frequency for different band gap energies, temperature and carrier densities, are described. In another study, variations of the electron and hole densities are simulated and the resulting integrals are evaluated numerically. The changes of carrier density in an intrinsic GaAs semiconductor as a function of the position of the quasi-Fermi levels in the conduction or valence bands for different temperatures, are also reported. For GaAslaser, accurate normalized densities are obtained as a function of temperature. The normalized densities at T = 3000Kare at the ratio of 1.98:1:0.4for T = 200,300and 400oK, respectively. The peak gain values, normalized at the same room temperature, are at the ratio of 2.05:1:0.36, for T = 200,300 and 400° K, respectively. Comparing the results presented for the carrier density and gain, with other studies, this method provides an accurate result. It is noted that temperature has a dominating effect on the gain profile and, as a result, on the laser overall performance as observed in the experiments.

This paper presents equivalent circuit models for both relative intensity noise (RIN) and phase/frequency noise spectrum (FNS) in a single semiconductor laser diode. The model for the electrical phase noise of a single mode laser is proposed for the first time. These equivalent circuit models are derived from the rate equations including the Langevin noise sources. Then, RIN and FNS are calculated in terms of electrical parameters. Finally, we explain an indirect experimental method used to measure RIN and FNS of a typical optical communication laser diode. Behavior of the experimental results is in agreement with those calculated by circuit models.

The interaction of the cavity electromagnetic field with the two-level emitter is described by cavity quantum electrodynamics (CQED). A pulsed micro-laser is an array of semiconductor quantum dots (QDs) embedded in an optical micro-cavity. This is one of the basic tools of quantum information technology. In this study, the energy eigenvalues variations and the quantum efficiency of a micro-laser system includes a QD with a decay rate of 0. 8μ eV embedded in the different micro-cavities, were investigated. The results show that with the increasing coherent interaction rate of micro-laser system, the energy eigenvalues variations of this optical system also increase. The quantum efficiency for this nano-optical system was studied. The results show the smaller micro-cavity decay rate, the higher quantum efficiency at smaller coherent interaction rate. Then, the optimal value of the micro-cavity decay rate was obtained in order to achieve the maximum quantum efficiency. The calculation results showed that the highest quantum efficiency occurs for optical parameters γ a=0. 8μ eV, g=95μ eV, γ c=177. 7μ eV, and η max=0. 991.

In this paper, the performance of a ring laser Gyro based inertial navigation is investigated. Dynamic and stochastic modelings are applied to gyro simulation and performance evaluation. In the dynamic model, some parameters such as scale factor and environmental sensitivity have been determined, whereas in the stochastic model, the other parameters such as random drift and measurement noise have been computed. The performance of the system is evaluated for several inputs. Also, the parameter variation of output noise as a result of changing the dither characteristics is analyzed.