PMD measurement results and theory of a single waveplate are presented. A commercially available waveplate is meas-ured, using a new instrument that allows one to distinguish the intrinsic PMD of the waveplate material from mixed effects, and to retrieve the relevant parameters through multi-resolution analysis. This illustrates, in the most simple case, a generally unexpected PMD behavior that can be observed in multipath optical components. Emphasis is put on the basic need to carefully choose, or at least specify, the resolution bandwidth of PMD measurements. This proves necessary not only to understand the results, but also to characterize PMD-induced pulse spreading.
A new implementation of the modulation phase-shift technique is presented that is well adapted for field use. The method uses measurements of modulation amplitudes to compute relative group delays (RGD). Unlike existing phase-shaft-method implementations, this technique requires no control or calibration of relative phases in the electrical domain. For RGD measurements, a broadband LED emitter - tunable filter receiver combination is used. With this simple set-up, ten RGD measurements taken at 16 different wavelength points (i.e. over 160 measurements) gave standard deviations of 2 to 6 ps. Standard fiber (non-zero dispersion shifted) lengths of over 160 km are accurately measured.
The critical aspects of signal sampling in the context of optical measurements are reviewed. A parallel is drawn between optical- and time-signal sampling, which shed light on the impact and interplay between key parameters. All key parameters have their mirror image in both pictures, time ? frequency or optical-frequency ? optical-delay. The equivalence is made specific, between optical sampling-step, resolution bandwidth, interferograms, photodetector bandwidth or laser lineshape on one hand, and sampling rate, low-pass filter, signal spectrum and signal bandwidth on the other hand, along with the conditions they should fulfill, in both pictures, given an actual setup.
We describe the principle of an instrument for PMD determination over nearly four orders of magnitude, from under 10 fs to 40 ps, through an adaptive combination of three standard PMD measurement methods: the interferometric, fixed analyzer, and Poincare sphere methods. The key elements in this adaptive instrument are a conventional interferometric PMD analyzer and a rotating polarizer. The fringe patterns, obtained with a few settings of the rotating polarizer, are used to perform either a direct time-domain analysis or a frequency-domain analysis after Fourier transform.
We report the progress of our work on the observation and the characterization of 87Rb vapor resonances in order to frequency-lock a 1529 nm DFB semiconductor laser. We present energy levels diagrams corresponding to the 5P3/2 yields 4D5/2 and 4D3/2 transitions of rubidium atoms, respectively at 1529.4 and 1529.3 nm (196.02 and 196.04 THz). Basic emission characteristics of our DFB laser are also given. We then show the absorption profiles of a probe laser emitting around 1529 nm while the 87Rb vapor is optically pumped at 780.2 nm (D2 line at 384.2 THz) using a 30 mW AlGaAs laser. We finally present, for this experiment, the dependence of the probe laser absorption resonance depth and linewidth on the pump power.
Recently we demonstrated a technique to achieve the absolute calibration of a Fabry-Perot resonator used as a multi-frequency discriminator with evenly distributed reference values. These references are used to frequency-lock an ensemble of laser sources to precisely known values. We present in this paper a summary of the procedure that we established and discuss the frequency setting capability and the accuracy of such an optical frequency generator.
We describe a simple method to produce a clock transition with purely optical means through modulated pumping. We observe the field-independent ground state resonance of 87Rb atoms using sinusoidal modulation of the injection current of an AlGaAs laser diode emitting at 780 nm (FM modulation). We detect the 6.835 GHz resonance with a modulation frequency of 1.139 GHz. A high contrast resonance peak is observed and a condition for zero light shift is found. With a beam radius of approximately 3 mm and a buffer gas (N2) pressure of 680 Pa (5.1 Torr), a minimal linewidth of 290 Hz is observed. A theoretical study of the excitation of hyperfine coherences by a modulated laser beam is given.
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