These constrains define limits of applicability of time-averaged laser holography in engineering applications. The laser wavelength if usually a fixed constant (�� = 632.8 nm, for HeNe laser). Thus one must pre-assess the results of the optical experiment.All schematic diagrams in figure are based on the assumption that the FTY720 IC50 illumination and the observation directions are perpendicular to the plane of the beam in the state of equilibrium (in the par-axial model). In general case the distribution of
The work is motivated by the fact that with the advent of fully digital telecommunications in the past decade, the real-time digital signal processing in the radio frequency (RF) domain has quickly moved from theoretical outlines to engineering practice.
This has allowed replacing some blocks of traditional analog electronics by software algorithms in many types of servo-loops. A similar situation is seen in the fundamental metrology of precise time and frequency. These quantities are processed very often by optical frequency combs which Inhibitors,Modulators,Libraries have become important instruments in the field of measuring optical frequencies of continuous-wave (CW) laser sources [1]. These instruments are also called optical frequency synthesizers because they are able to transfer the relative stability of RF signals to the optical frequency domain and vice versa [2,3].In principle, the optical frequency comb is based on a femtosecond mode-locked laser. It generates a train of pulses, which Inhibitors,Modulators,Libraries from the signal processing point of view is an optical-frequency carrier modulated by a radio-frequency (RF) pulsed envelope.
Pulse widths are typically in the range of tens of femtoseconds up to 1 Inhibitors,Modulators,Libraries ps. According to signal processing theory, such waveforms are transformed into a set of evenly spaced components in the frequency domain. The spacing of these components is equal to the repetition frequency frep of the pulses and the offset of these pulses with respect to zero is dependent on the carrier-to-envelope frequency, the so called offset frequency fceo. Hence the output of a system like this can be seen as a set of many lasers working synchronously at the same time at evenly spaced optical frequencies. The optical frequency of a certain spectral component ��i can be easily described by the following formula [4]:��i=fceo+i?frep(1)where i is the index of the spectral component; frep is usually from tens to several hundreds of MHz and fceo is in the range from 0 Hz to frep.
The width of the optical spectrum of generated femtosecond pulses Inhibitors,Modulators,Libraries depends mainly on the width of a gain spectrum profile of the active media of the mode-locked laser. Incase of an infrared Er3+ doped Batimastat fiber femtosecond laser the output spectrum is typically 200 nm wide and finds itself ARQ197 FDA around a 1550 nm central wavelength [5,6].The transfer of the relative stability of a radiofrequency signal to the optical domain is based on this technology of femtosecond optical synthesizers [7,8].