Laser Wavelength Control Research Articles

Intelligent Modeling for Transfer Function Control of DBR Semiconductor Laser at Near-Working Point

In this paper, a novel intelligent modeling method for transfer function control of DBR semiconductor lasers at near-working point is proposed, which is based on the quantum particle swarm optimization (QPSO) algorithm. This modeling method effectively solves the difficulty of application in the traditional laser theory and equivalent circuit models in practical engineering. First, we analyze the input and output characteristics of DBR semiconductor laser at near-working point, where the laser system can be equivalent to a transfer function model including two main modules: the laser power control module and the laser wavelength control module, and determine the structure of this equivalent model based on the analysis results. Then, we use the QPSO intelligent algorithm to identify the model parameters and finally obtain the equivalent transfer function model that can be easily applied to practical engineering. The standard deviations of the steady-state errors of these two modules are 3.4×10 -3 and 1.2×10 -5 , respectively. Experiments verify the effectiveness and convenience of the proposed (intelligent modeling) method, which can be used for on-line modeling of the DBR semiconductor laser at near-working point.

Ultra-compact all-in-fiber-core Mach-Zehnder interferometer.

Optical Mach-Zehnder interferometers (MZIs) are useful components in a variety of optical applications, including optical modulation; signal processing; and physical, chemical, and biological sensing. We introduce here a novel, assembly-free all-in-fiber-core MZI, which is directly written with a femtosecond laser. By introducing a positive refractive index-modified zone in half of the fiber core, the original single-mode fiber section is converted into a few-mode fiber section, where a strong coupling between the two lowest-order guided modes is generated, resulting in a well-defined interference spectrum in transmission. This device promises many significant advantages over existing approaches such as ease of fabrication, stability, small insertion loss, robustness extremely broad operating bandwidth, and precise and controllable cavity lengths. These advantages make this device strikingly attractive with the potential for extensive adoption in fiber communications, signal processing, sensors, and laser wavelength control.

Fabrication and applications of volume holographic optical filters in glass

We review the applications of glass volume holographic filters and a manufacturing and testing method. During the last few years, such filters have found commercial success in fields such as laser wavelength control, beam combining, Raman and astronomy filters.

Laboratory, ground-based, and airborne tunable diode laser systems: performance characteristics and applications in atmospheric studies

O) used as the target gas. One method utilizes the Allan variance. When our present aircraft system is operated in the laboratory, the Allan variance indicates a CH2O detection limit of 0.031 ppbv for integration times of 25 s. This sensitivity corresponds to a minimum detectable absorbance of 1.0×10-6, and this is within a factor of two of that reported by Werle et al. who used high-frequency modulation spectroscopy. The present instrument utilizes conventional low-frequency (2f=100 kHz) wavelength modulation. Instrument performance, obtained from replicate measurements of CH2O standards acquired over time periods as long as 1.5 hours, on average resulted in a factor of two poorer precision than indicated by the Allan variance. Since replicate measurements precisely simulate the acquisition procedures employed, including the acquisition of sample and background spectra, they present a more meaningful measure of instrument performance. Preliminary evidence suggests that slow drifts in the laser wavelength control during acquisition of replicate measurements may play an important role in the above disparity. The resultant laser wavelength correction voltage, which is applied to counter such drifts, may also be a factor in this disparity. A limited number of replicate measurements with minimal drift in the laser wavelength yield much closer agreement between replicate and Allan variance precisions.

Tunable diode laser wavelength control by a Michelson interferometer

The wavenumber λ d of a tunable diode laser (TDL) is actively forced to preserve its interference order k d through a Michelson interferometer with a path difference D ( D = k d × λ d). This path difference and its variation ΔD are controlled by a stabilised He Ne laser. A change ΔD induces λ d to change by an amount Δλ d. This procedure reduces by two orders of magnitude the usual jitter of a TDL wavenumber emission. Several applications of this precise instrument (line shifts, line mixing effect, deconvolution of denses spectra) are given.

Special Issue on Laser Parameter Control. Dye Laser Wavelength Control System for Uranium Isotope Separation.

Copper vapor laser pumped dye laser systems are being developed for Atomic Vapor LaserIsotope Separation (AVLIS). Function of dye oscillator is tuning its wavelength to absorptionline of Uranium. Precise tunability, high accuracy and also high efficiency are required for theoscillator, in order to separate trace Uranium 235 isotope from Uranium 238. To fulfill suchconditions, single axial mode dye oscillator with frequency-chirp is developed. This paper reviewsthe present status of wavelength control system in pulsed dye laser for AVLIS process.

Practical realization of a high density diode-coupled wavelength demultiplexer

The design, development, and optical performance of a novel demultiplexer in which a photodiode array replaces the array of fibers at the output is described. The prototype diode-coupler high-density wavelength demultiplexer has 16 channels with 4-nm channel spacing. Its optical performance, with respect to insertion loss, optical passband, total optical crosstalk, and polarization response and taking into account expected component and manufacturing tolerances is good. In particular, an optical passband between +or-0.7 nm and +or-0.9 nm can be tolerated without deterioration in performance, reducing the need for precise laser wavelength control. In addition, the diode leakage currents achieved, although relatively large, do not constitute a significant penalty in receiver sensitivity for applications at 560 Mb/s or higher, and the diode capacitance is very low. It is concluded that this is an attractive solution for high-density wavelength-division multiplexing. >