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Vertical cavity surface emitting laser VCSEL is currently the main solution for many technological aspects, ultrafast optical interconnecting, Gigabit Ethernet, etc. In this paper we present the simulation results by using Optiwave™ software version 7, of the effects of optical mode confinement factor on the modulation properties)which inspected by eye diagram of the received signals)of the vertical cavity surface emitting laser VCSEL, with the range (8-20)Gbps of pseudo random bit sequence PRBS. The quality of the VCSEL modulation have been inspected by time domain signals, spectrums and eye diagram. Simulation results appeared an improvement in the characteristics of received bit sequences of (8, 10, 12.5, 16 and 20)Gbps bit rates, represented by the rising the value of quality factor QF (1.77 to 4.81) versus increasing the value of optical mode confinement factor Γ(0.2 to 0.5) respectively, and a decreasing in jitter time of superimposed traces of eye pattern and well opining eye pattern. And in the corresponding, the bit error rates BERs of the received signals have been decreased, with rising the value of mode confinement factor Γ of the laser at constant modulation index and constant temperature of the laser. Also, the VCSEL’s modulation response differences with different bitrates, causes different values of QF and BER for individual value of mode confinement factor Γ.

Abstract: The electrical and optical characteristics of diode pumped solid state frequency doubled (DPSSFD) semiconductor laser had been studied. Five different techniques had been used to calculate the laser threshold are (L-I, V-I, dV/dI vs I, IdV/dI vs I, L/(dL/dI) vs I). The calculated values of threshold current had been found varying from 96mA to 99mA.While the series resistance of the laser diode was determined above threshold by using three methods (V-I, dV/dI vs I, IdV/dI vs I) and the value estimated between (6.3 ~ 6.6). The quantum differential efficiency  D had been found to be high and equal to 0.66W/A. Maximum optical power emitted from DPSSFD laser is 14mW.The electrical ideality factor and optical ideality factor should be nearly equal and they are about unity.

Abstract: The effects of semiconductor laser light on static and dynamic characteristics of bipolar exposed transistor had been studied experimentally. There was no significant influence on these characteristics in the absence of semiconductor light on transistor device. Analog optical modulation of bipolar transistor had been realized with semiconductor laser light direct modulation, while there was evident effect of injection current of semiconductor laser on the harmonic of spectrum modulation of transistor output. Optical modulation of bipolar transistor had been realized using pulse width modulation technique, and there was no deformation in pulse shape out from collector of the transistor modulated by small duration time pulses. Deformation in pulse shape out of the bipolar transistor has been observed when semiconductor laser modulated by large duration time pulses that is decrease qualification of data transfer.

Abstract The experimental fulfillment for optical bistability in a semiconductor laser under injection locking is studied. The required setup to provide the stability in current, temperature and power output of the laser diode used in experiments has been described in detail. A small change in the injection power of the slave laser SL could induce a dynamic change of the lasing power of the master laser ML has been observed. Optical bistability for two non identical laser was possible has been experimentally observed.

Abstract Effect of optical feedback (O.F) on AlGaInP semiconductor laser properties and intensity modulation has been studied experimentally. Threshold current of semiconductor laser decreased 1mA when O.F equal to 160W , while there is no significant decreases observed in threshold current both when increasing O.F above that value or less than it. Influence of O.F on amplitude modulation spectrum at frequencies modulation (0.123,0.246, 0.546, 1.2)MHz has been studied. Fundamentals harmonic spectrum peaks increased with O.F especially at frequency modulation (1.2)MHz , whereas opposite effect of O.F observed on Fundamentals harmonic spectrum peaks at frequency 132kHz, since it decreased with O.F . O.F participate in decreasing of relative intensity noise (RIN) just at frequencies modulation(0.264, 0.546, 1.2)MHz with appearance of Flicker noise at frequency 132kHz. Signal to noise ratio (SNR) increased with O.F especially at frequency modulation equal to 1.2MHz has been observed.

Abstract A laser sensor was designed in this work in order to detect water vapour and some chosen gases for the enviromented pollution or in the field of meteorology . The gases that had been studied were , , and . The results had been pointed out that the gas gave the lowest attenuation on laser radiation , while the gas the largest attenuation . we were able to detect the of an amount (23.5) part in athousant of volume when passing through the gas chamber in per second .

Abstract Characteristics of direct modulation of semiconductor laser microwave frequency were studied using the spectrum analyzer. The study showed the frequency distortion was greatly affected by the index of modulation, the laser diode temperature and the modulating frequency. The results indicated that the increase of distortion with frequency was found to be as (0.84 dB/MHz). On the other hand, the dependence of distortion on the index of modulation (m) showed that (m≤ 0.5) in order to keep the distortion as low as possible and a linear operation of laser diode.

Noise spectra of semiconductor laser subject to a phase-conjugate feedback were investigated theoretically. Time-delayed rate equations with feedback were solved and characteristic equations for relative intensity noise and frequency noise spectra were derived. Numerical results indicate that the relaxation resonance peak was moved to a new frequency region determined by the amount of feedback, This is a technological importance for the improvement of modulation bandwidth, Noise level was affected by the feedback parameters, mainly; the response time and the feedback rate.