A spectral optical code division multiple access transmission system using forward error correction is demonstrated. Matching channels are recovered error-free with 15 channels operating at 155.52 Mbit/s and up to eight channels operating at 622.08 Mbit/s.

Quasi-phase-matched (QPM), i efficient second-harmonic generation (SHG) using periodic reversals in the sign of the nonlinear coefficient to compensate for dispersion has recently been demonstrated in bulk’ as well as in waveguide devices.3B4 QPM allows interactions between waves polarized such that the nonlinearity is maximized and allows interactions in materials for which birefringent phase matching is not possible, e.g., SHG of blue light in LiNb03. First-order QPM requires sign reversals of the effective nonlinear coelhcient with a period equal to two coherence lengths. Alternating ferroelectric domains have been achieved in LiNb03, LiTa03, and KTiOP04 (KTP) by modulating the dopant concentration during growth,5 indiffusing dopants,4V6 applying electric fields,’ or by techniques using electron beams8 or SiOZ masks.s In LiNbO,, QPM allows nonlinear interactions between waves polarized along the z axis, for which the largest nonlinear coetlicient d,, = 2d&n= 20.9 pm/V can be used.” In practice, the creation of the required, finely spaced domains with sufficiently accurate periodicity is a challenging task. I1 Feng et al. produced Czochralskigrown LiNb03 crystals doped with 0.5-l wt. % yttrium with domain lengths of 3.4 ,um to frequency double the 1.064 ,um Nd:YAG laser line.12 The observed conversion efficiency increased quadratically with the crystal length as expected for perfect domain periodicity up to lengths of about 680 pm, corresponding to 200 domains. For longer crystals the increase was linear, revealing domain-boundary position errors on the order of the coherence length. These position errors are probably caused by variations in growth speed due to thermal fluctuations during the Czochralski growth. The laser-heated pedestal growth methodI can be used to grow miniature crystal rods with good control of the average growth speed and thus the domain period. To start the growth, a COz laser is focused on the tip of a source rod to make a small molten droplet into which a seed crystal is dipped. The location of the freezing interface during growth is determined by the thermal properties of the zone and the location of the heating laser focus. The small dimension of the molten zone and the large thermal gradients in this growth result in a freezing interface with a precisely controlled position. The domain periodicity,

We have demonstrated wide-bandwidth photodetector power combining in a structure we call the traveling wave detector array (TWDA). The TWDA embeds several small discrete optical detectors within a microwave quasi-transmission line (QTL) structure that coherently combines their RF photocurrents while maintaining the bandwidth of a single detector

Analog fiber-optic links are used in a variety of microwave applications, The RF insertion loss and RF output power available from these links is currently limited by photodetector optical power handling, Using traveling-wave concepts similar to those in distributed amplifiers, we have demonstrated traveling-wave detector arrays (TWDA's) in which photodetectors are embedded within an artificial transmission line. By feeding this network with suitably time-delayed optical signals, this arrangement coherently combines the RF photocurrents from two detectors, yielding a 6-dB improvement in insertion loss and RF output power, while retaining 12 GHz of operating bandwidth.

Analog filter-optic links are used in a variety of microwave applications, including cable-TV and cellular-telephone distribution as well as antenna remoting, The RF insertion loss and output power obtainable from externally modulated links is primarily limited by photodetector optical-power handling capabilities, Using traveling-wave concepts similar to those in microwave distributed amplifiers, we demonstrate the principle of traveling-wave detector arrays (TWDA's) in which discrete photodiodes are embedded within an artificial transmission line, By feeding these detectors with suitably time-delayed optical signals, this arrangement coherently combines multiple RF photocurrents into a single output, This paper presents the theory, construction details, and results of two-and four-element TWDA's operating up into the Ku-band, We demonstrate a two-element TWDA yielding a 6-dB improvement in insertion loss and RF output power with 12 GHz of operating bandwidth, and a four-element TWDA yielding 12-dB improvement up to 18 GHz.

Quasi-phase-matched room-temperature frequency doubling to generate blue, green, and red light was demonstrated using periodically poled LiNbO3 crystals. A 1.24-mm-long sample in an external resonant cavity generated 1.7 W of green power from an input of 4.2 W at the 1.064 μm Nd:YAG laser line when heated to 140 °C to compensate for a slight error in periodicity.

Quasi-phase-matched room-temperature frequency doubling to generate blue, green, and red light was demonstrated using periodically poled LiNbO3 crystals. A 1.24-mm-long sample in an external resonant cavity generated 1.7 W of green power from an input of 4.2 W at the 1.064-mu-m Nd:YAG laser line when heated to 140-degrees-C to compensate for a slight error in periodicity.

Quasi‐phase‐matched room‐temperature frequency doubling to generate blue, green, and red light was demonstrated using periodically poled LiNbO3 crystals. A 1.24‐mm‐long sample in an external resonant cavity generated 1.7 W of green power from an input of 4.2 W at the 1.064 μm Nd:YAG laser line when heated to 140 °C to compensate for a slight error in periodicity.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text G. A. Magel, E. J. Lim, M. M. Fejer, and R. L. Byer, "Second harmonic generation in periodically-poled LiNbO3," Optics News 15(12), 20-21 (1989) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Single-crystal sapphire (α-Aℓ203) fibers are potentially useful in a wide variety of optical applications, particularly those involving high-power or high temperature light-guiding, over the wavelength range from 0.24 μm in the ultraviolet to 4.0 μm in the mid-infrared. These fibers are routinely grown at rates of up to 8 mm/min, and with diameter stability of better than 0.5% rms under feedback control. Recent measurements on unclad 150 μm diameter fibers show fundamental mode scattering losses of about 0.3 dB/m in the visible and less than 0.07 dB/m at 3.39 μm.

A fiber diameter variation measurement system is described which is capable of measuring transparent fibers with 0.02% diameter resolution and 6-microm axial resolution at a measurement rate of 1 kHz and with a working distance of >100 mm. The principles of its operation are discussed in detail, and experimental confirmation of its performance is reported. A theoretical calculation of the optimum obtainable diameter resolution for a given set of experimental parameters is also presented.