An overview of analog microwave photonics will be presented. The performance requirements for externally-modulated analog microwave photonic links will be reviewed with specific emphasis placed on modulator efficiency, laser noise, detected photocurrent, and link linearity.

http://ieeexplore.ieee.org/iel5/6387506/6403300/06403360.pdf

Microwave photonics

An inversion algorithm, involving a linear least-squares method, is developed to analyze the intensity data obtained by application of the traveling knife-edge method. Through use of simulated intensity data, diameters can be measured to an accuracy of 0.05%. The method also yields good results when it is applied to He–Ne laser beam data.

Measurement of a Gaussian laser beam diameter through the direct inversion of knife-edge data

To better understand DNA photodamage, several nucleosides were studied by femtosecond transient absorption spectroscopy. A 263-nm, 150-fs ultraviolet pump pulse excited each nucleoside in aqueous solution, and the subsequent dynamics were followed by transient absorption of a femtosecond continuum pulse at wavelengths between 270 and 700 nm. A transient absorption band with maximum amplitude near 600 nm was detected in protonated guanosine at pH 2. This band decayed in 191 ± 4 ps in excellent agreement with the known fluorescence lifetime, indicating that it arises from absorption by the lowest excited singlet state. Excited state absorption for guanosine and the other nucleosides at pH 7 was observed in the same spectral region, but decayed on a subpicosecond time scale by internal conversion to the electronic ground state. The cross section for excited state absorption is very weak for all nucleosides studied, making some amount of two-photon ionization of the solvent unavoidable. The excited state life...

DNA Excited-State Dynamics: Ultrafast Internal Conversion and Vibrational Cooling in a Series of Nucleosides

The low-loss wide-bandwidth capability of optoelectronic systems makes them attractive for the transmission and processing of microwave signals, while the development of high-capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics. This paper describes the development of microwave photonic devices, describes their systems applications, and suggests likely areas for future development.

where co is the angular velocity of the chopper, r the distance from the rotating center to the laser beam axis, and t2-t, the time interval for a variation of P(x)/P0 from 0.9 to 0.1. Figure 1 shows the experimental arrangement. In this experiment, we use a He-Ne laser oscillating in the TEMoo mode. The wavelength is 0.63 m. The position of the beam waist is located at the output mirror of the laser oscillator, and the beam radius w, at the waist is 0.4 mm. The focal length of lens A is 367 mm. The distance from lens A to the output mirror surface of the laser is 600 mm. Lens A transforms the beam from the oscillator to a beam that has a more accessible waist. The radius and the posi-

Measurement of the microm sized radius of Gaussian laser beam using the scanning knife-edge.

Technique for Fast Measurement of Gaussian Laser Beam Parameters

An 11-GHz optical modulator using LiTaO3 as the electrooptic material has been designed and built. The experimental model has a bandwidth of about 100 mHz and is tunable over 1.5 GHz with uniform modulation characteristics. A phase modulation index of 0.45 rad was achieved with 1.6 W of modulating power.

G. D. Mandeville

Papers

Technique for Fast Measurement of Gaussian Laser Beam Parameters

Performance of an 11-GHz Optical Modulator Using LiTaO(3).