Single Stage Faraday Isolators

Compact Isolators

Overview

The FI-x-2SV/-2SI and FI-x-5SV/-5SI compact isolators use a single stage Faraday isolator. The body length is kept to a minimum with the use of powerful permanent magnets in an optimized geometry. A 360° rotation of the exit polarizer provides a maximum extinction over a certain range of the central wavelength. The entrance and exit polarizers are polarizing beam splitter cubes. The blocked radiation is diverted through 90° and is readily available for other applications. At 30dB, the specification of the isolator is sufficient for most standard applications. For specialized applications, selected isolators with an extinction of 45dB are available.

A higher extinction is provided by the models DLI or FI-x-TV/-TI.

Wavelength tuning

The Verdet constant of the TGG crystals is dependent upon wavelength and temperature. Therefore it is neces­sary to tune the isolator in order to achieve maximum extinction. Tuning the isolator is accomplished by rotating the holder of the exit polarizer with respect to an angular scale. The graph shows the reduction factor of the transmission, T(Δλ), that is due to the tuning of the isolator to a wavelength λ that is different from the design wavelength λ₀. The bar has a length that covers the wavelength range for which 0.95 < T(Δλ) < 1. The bullet indicates the design wavelength λ₀. The overall transmission of a Faraday isolator is equal to T_t = T₀ x T(Δλ), where T₀ is a factor that represents the transmission of the polarizers. At the design wavelength the overall transmission of the Faraday isolator is T₀ > 90 %. An individually calibrated adjustment diagram is delivered with each isolator as an aid for wavelength tuning.

BB-option

The rotational dispersion of the Terbium Gallium Garnet crystal (TGG) can be compensated by an additional op­tion BB. This renders the device usable over a wavelength range of ±100nm without additional adjustment. The isolator also functions with broadband spectral beams. The BB option also allows the user to choose between a broadband compensated isolation or a broadband com­pen­­sated transmission.

The modular isolator concept allows for the upgrading of the standard isolator FI-x-5SV to a broadband version FI-x-5SV-BB.

The isolator can be mounted on rods, cylindrical mounts or by using the assembly surfaces so that the laser polari­zation can be oriented horizontal or vertical.

Applications

These isolators are suitable for all lasers operating in the 500–900nm wavelength range especially:

Ar+ and Kr+ lasers 
other Ion lasers
HeNe lasers 
other Gas lasers
Dye lasers Diode lasers
Ti: Sapphire lasers 
Cr:LiCAF lasers
Short Pulse lasers 
Mode-synchronized lasers
Alexandrite lasers