Electrooptical modulators

Materials are also classified according to a particular phenomenon being considered. AppHcations exploiting off-resonance optical nonlinearities include electrooptic modulation, frequency generation, optical parametric oscillation, and optical self-focusing. AppHcations exploiting resonant optical nonlinearities include sensor protection and optical limiting, optical memory appHcations, etc. Because different appHcations have different transparency requirements, distinction between resonant and off-resonance phenomena are thus appHcation specific and somewhat arbitrary. 

Materials for Electrooptic Modulation. The fundamental phenomenon of Pockel s effect is a phase change, A( ), of a light beam in response to a low frequency electric field of voltage, V. Relevant relationships for coUinear electrical and optical field propagation are as foUows (1 6) ... 

Two parameters that characterize the performance of electrooptic modulators are k E and the bandwidth given by the following ... 

Table 1. Comparison of Electrooptic Modulator Performance Parameters of NLO Materials ...

A market for electrooptic modulators does not exist as of this writing much of the motivation for developing prototype devices derives from anticipated needs of the information superhighway and the cable television industry. Various corporate research laboratories have produced prototype modulators that can operate to 60 GH2 (7,19—28). Nontechnical issues such as the early implementation of direct (satellite transmission) television may also affect the market success of these electrooptic modulators. 

Electrooptic displays, liquid crystal polymers in, 75 110 Electrooptic effect, 74 675 Electrooptic modulation, second-order nonlinear optical materials for, 77 444... 

Electrooptic modulators, 74 675-676 market for, 7 7 448 performance of, 7 7 446 Electroorganic reaction, 9 652 Electroorganic systems, diaphragms in, 9 656... 

Ilchenko, V.S., Matsko, A.B., Savchenkov, A.A., Maleki, L., 2002, High-efficiency microwave and millimeter-wave electrooptical modulation with whispering-gallery resonators, Proc. SPIE 4629 158-163. 

Figure 17. (a) Transverse electrooptic modulator that rotates polarization of an incoming light beam as a function of applied electric field and (b) a travelling Mach-Zehnder interferometer that introduces a phase shift to the light beam in one arm as a function of applied field. 

Recent advances in optical technology have created great interest in the construction of second-order nonlinear optical (NLO) devices for frequency conversion and electrooptic modulation. Although inorganic substances such as LiNbO possess strong second-order NLO properties and... 

Modulation can be accomplished in a variety of ways. For example, the output of a laser can be modulated directly or external modulation can be applied using electro-optic or electro-absorptive modulators. Currently, commercial electrooptic modulators are fabricated from lithium niobate. The performance characteristics of one family of lithium niobate modulators, produced by Lucent Technologies (Breinigsville, PA), are given in Table 1. 

The measurement of optical activity in Raman spectra is most often done by measuring the circular intensity difference (CID) and the circular intensity sum (CIS). Using this technique the linearly polarized la.ser beam used for excitation is modulated with a KD P electrooptical modulator resulting in an excitating beam which changes its state of polarization from left to right circularly polarized at a frequency of about 1/3 Hz. The Raman intensities are then collected separately and the dimensionless Raman CID calculated using ... 

The depolarized spectra were taken employing a 90 ° scattering geometry on a Ramanor HG.2S (Jobin-Yvon) scanning Raman spectrometer using a KD P electrooptic modulator and 1 Watt of the 488 nm Argon ion laser line. 

Fig. 5 Block diagram for a commercial doublemonochromator CD spectropolarimeter. M = various mirrors S = slits P = polarizing elements LS = light source SC = sample PMT = photomultiplier tube L and F = lens and filter, respectively EOM = electrooptic modulator.

In contrast, the nonlinearities in bulk materials are due to the response of electrons not associated with individual sites, as it occurs in metals or semiconductors. In these materials, the nonlinear response is caused by effects of band structure or other mechanisms that are determined by the electronic response of the bulk medium. The first nonlinear materials that were applied successfully in the fabrication of passive and active photonic devices were in fact ferroelectric inorganic crystals, such as the potassium dihydrogen phosphate (KDP) crystal or the lithium niobate (LiNbO,) [20-22]. In the present, potassium dihydrogen phosphate crystal is broadly used as a laser frequency doubler, while the lithium niobate is the main material for optical electrooptic modulators that operate in the near-infrared spectral range. Another ferroelectric inorganic crystal, barium titanate (BaTiOj), is currently used in phase-conjugation applications [23]. 

Chopping their CW intracavity doubled ring laser with an electrooptical modulator van Herpen et al.9 obtained 40 nsec pulses with a spectral width of about 25 MHz. This allowed them to study the decay of a single molecular eigenstate. Figure 6 shows a typical result of such an experiment. As might... 

Nanosecond laser has been used with good quality, durability electrooptical modulator collected on the ground of yttrium orthoaluminate with Nd (III). The 3-rd ground emission has the follouing parameters X = 360 nm, Eimp = 3.0 mj, x imp=20 ns, v =5.0 Hz, the beam diameter on the substrate sample 1 mm. The experimental data are collected and worked up by means of special microcomputing system which is marked in the figure s 2 subscription, In all cases... 

Figure 3. (a) Schematic diagram of the Brookhaven transient FM spectrometer, in which EOM = electrooptic modulator and SA = spectrum analyzer, (b) Schematic diagram of the FM detection electronics, in which LO = local oscillator, L pass = low pass filter. [Reprinted with permission from S. W. North, X. S. Zheng, R. Fei, and G. E. Hall, J. Chem. Phys., 104(6), 2129-5. Copyright 1996 American Institute of Physics.]... 

Figure 31. (a) ATR electrooptical experimental setup, and (b) an example of the record of electrooptic modulation. 

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