Iraqi Journal of Laser

Discrete Raman amplifier have many attractive aspects over rare-earth doped fiber amplifier such as (EDFA) including arbitrary gain band, better adjustability of gain shape, and better linearity. This paper shows that discrete Raman amplifier has higher gain in bidirectional pumping than counter pumping. The gain increases with increasing fiber length, and the noise figure remain at the same value for short fiber length

A characteristic study of a passively Q-switched diode pumped solid state laser system is presented in this work. For laser a comparison study for the theoretically calculated results with a simulation results using a software which calculates the Q-switched solid state laser parameters was such as energy, peak power and pulse width were performed. There was a good agreement between our theoretical calculations and the simulation values

This research investigates new glasses which are best suitable for design of optical systems working in the infrared region between 1.01 to 2.3μm. This work is extended to Oliva & Gennari (1995,1998) research in which they found that the best known achromatic pairs are (BAF2-IRG2; SRF2-IRG3; BAF2-IRG7; CAF2-IRGN6; BAF2-SF56A and BAF2-SF6). Schott will most probably stop the production of these very little used and commercially uninteresting IRG glasses. In this work equally good performances can be obtained by coupling BAF2, SRF2&CAF2 with standard glasses from Schott or Ohara Company. The best new achromatic pairs foundare (SRF2-S-TIH10; CAF2-S-LAL9; CAF2-S-LAL13 and CAF2-S-BAH27). These new achromatic pairs are analyzedby using ZEMAX ray tracing program to design and analyzethe same F/2 camera used by Olivaandforthe same near infrared region (1.01-2.3μm). The results show that these pairs of glass have good performance in infrareddesignapplications.IntroductionA lens which is corrected for only one wavelength (color) -e.g. for laser applications -is described as a monochromat, i.e. the monochromatic aberration has been corrected, while chromatic aberrations remain uncorrected. Most lenses for general photography, laser to fiber coupling and wavelength-division multiplexing applications, however, are usedin a broader spectrum (wavelength range). Thus the chromatic (color) aberrations of these lenses must also be corrected over a wide spectrum to provide what is generally termed "sharpness". Here, the term "achromat" is used. Themost conspicuous color aberration is longitudinal chromatic aberration (LCA). With a monochromat, only the image (or the focus) of one wavelength lies in the image plane due to LCA, while the focus for shorter wavelengths lies in front of the image plane, and behind the image plane for longer wavelengths. Scientists say that "a primary spectrum is present". With an achromat, it is possible to correct the primary spectrum by combining converging and diverging lens elements made of different types of optical glass displaying different dispersion. To be more precise, it is possible to move the LCA for two wavelengths into the image plane (film plane).Optical designs of near-infrared (1.0–2.3μm) instruments are strongly constrained by a limited selection of near-infrared optical materials. Low-index materials such as CaF2, BaF2, LiF, NaCl, and infrared-grade fused quartz are commonly used forwindows and simple achromatic doublets. However, these low index materials have a restricted range of dispersive power that prevents good chromatic correction in complex, high-performance optical designs. In addition, NaCl, LiF, and BaF2 arehygroscopic and prone to damage. ZnSe isanother material that is suitable for near-infrared lenses, but its high index and large dispersive power limits itsusefulness. In addition, the high index of ZnSe makes it difficult to designbroadband antireflection coatings [1]. The internal transmission of most optical glasses with intermediate indices and dispersive powers is typically poor at near-infrared

In this work, the performance of the receiver in a quantum cryptography system based on BB84 protocol is scaled by calculating the Quantum Bit Error Rate (QBER) of the receiver. To apply this performance test, an optical setup was arranged and a circuit was designed and implemented to calculate the QBER. This electronic circuit is used to calculate the number of counts per second generated by the avalanche photodiodes set in the receiver. The calculated counts per second are used to calculate the QBER for the receiver that gives an indication for the performance of the receiver. Minimum QBER, 6%, was obtained with avalanche photodiode excess voltage equals to 2V and laser diode power of 3.16 nW at avalanche photodiode temperature of -10°C.

The simulation of passively Q-switching is four non –linear first order differential equations.The optimization of passively Q-switching simulation was carried out using the constrained Rosenbrock technique. The maximization option in this technique was utilized to the fourth equation asanobjective function;the parameters, γa, γcand β as were dealt with as decision variables. AFORTRAN program was written to determine the optimum values of the decision variables through the simulation of the four coupled equations, for ruby laser Q–switched by Dy+2: CaF2.For different Dy+2:CaF2molecules number, the values of decision variables was predicted using our written program.The relaxationtime of Dy+2: CaF2,used with ruby was calculated using the predicted value of γa.