Ultraviolet optical isolators utilizing KDP-isomorphs

Deep-ultraviolet (DUV) light sources are critical owing to their high photon energies and small diffraction limits, and synthetic quartz glass (SQ) is suitable for the Faraday rotators of DUV light. The Verdet constant in SQ was evaluated within the wavelength range of 190–300 nm. In addition to a high Verdet constant over the DUV region, this material exhibits a high transmittance without transitional absorption bands. The Verdet constants were found to be 70.1 rad/(T·m) at 193 nm, which is the shortest observed wavelength for silica glass. SQ glass has excellent structural properties; thus, it is suitable as a DUV Faraday rotator for high-average-power optical isolators.

Wavelength dependence of the Verdet constant in synthetic quartz glass for deep-ultraviolet light sources

The dispersion of the Verdet constant of LiY 1.0-x Er x F 4 crystals was evaluated from 190 nm to 500 nm for different doping concentrations of Er ions. A 15% doping concentration yielded a high Verdet constant of 54.5 rad/(T·m) at 193 nm. This value can be explained by the contribution of the diamagnetic term associated with LiYF 4 and the paramagnetic term of the Er ions. Although the LiYF 4 crystal yielded a lower value of −36.6 rad/(T·m) at 193 nm from Er-doped LiYF4, it can be used in the vacuum–ultraviolet region because of its high transmittance at wavelengths longer than 120 nm. 

Effect of erbium concentration on the Verdet constant dispersion of LiY<sub>1.0-x</sub>ErxF<sub>4</sub> single crystal

Verdet constant dispersion in synthetic quartz was evaluated with DUV light sources. The Verdet constant at 221 nm was determined to be 41.1 rad/Tm. The DUV optical isolator can realize with the moderate magnetic field.

Verdet Constant Dispersion Measurement of Synthetic Quartz in DUV Region

The Verdet constant in deep-ultraviolet region was evaluated and compared in synthetic quartz, LiY0.85Er0.15F4 and LiYF4. The DUV optical isolator can realize with the moderate magnetic field.

Comparison of materials for deep-ultraviolet optical isolator

A UV Faraday rotator for the high power KrF laser system and other UV excimer lasers has been developed for the first time. Pure water has high Verdet constant and high transmittance in UV region (up to 190 nm). Ninety degree polarization rotation of a KrF laser beam is obtained by passing through a 5 cm long quartz cell filled by pure water. Quartz rod has also been proved to be equally useful as a Faraday rotator for KrF lasers.

https://www.jstage.jst.go.jp/article/lsj1973/12/11/12_11_660/_pdf

Development of the UV Faraday Rotator

PURPOSE:To equalize a dielectric constant of the periphery of a magnetic field generating coil and to prevent a dielectric breakdown by using water as a Faraday rotary medium, and immersing the magnetic field generating coil into the water. CONSTITUTION:Ultraviolet rays which have been irradiated in the direction as indicated with an arrow B are polarized linearly by a polarizer 1 and transmit through in water 5. In this case, if a current I flows to a magnetic field generating coil 3, and a magnetic field H is applied to the water 5, when the ultraviolet rays transmit through the water 5, its plane of polarization rotates by 90 deg., becomes parallel to the polarization direction of a polarizer 2 and the ultraviolet rays pass through the polarizer 2. On the other hand, when the magnetic field generating coil 3 is not conducted electrically, the plane of polarization of ultraviolet rays does not rotate at all, when passing through the water, the plane of polarization of ultraviolet rays becomes orthogonal to the polarizating direction of the polarizer 2 and the ultraviolet rays are cut off by the polarizer 2. In this way, since the magnetic field generating coil 3 has been immersed into the water 5 filled in a sealed case 7, a dielectric constant of the periphery becomes uniform, an electric field concentration is not generated, and a dielectric breakdown can be prevented.

Kaminaga Takeshi

Papers

Development of the UV Faraday Rotator

Faraday rotary switch