What are 바카라 영어로 Rotators and Isolators?

Another important distinction is that the rotation angle produced by a 바카라 영어로 rotator is determined by the applied magnetic field. If an electromagnet (rather than a permanent magnet) is the source of this field, then the amount of rotation can be controlled electronically. In contrast, a half waveplate must be physically rotated to change the amount of rotation it produces.

What are Polarization and the 바카라 영어로 Effect?

To better understand what a 바카라 영어로 rotator does, it’s first necessary to take a step back and talk briefly about polarization. And to understand polarization we need to talk about the wave nature of light.

Light is an electromagnetic wave. Of course, we’re all famili바카라 영어로 with water waves. Imagine a stone thrown into a pond. The ripples that spread out across the water 바카라 영어로e waves. That is, they’re periodic v바카라 영어로iations in the surface height of the water that travel out from the center.

Now imagine that instead of waves that 바카라 영어로e ripples in water surface height, we have waves consisting of electric and magnetic fields. This means the strength of these fields changes periodically over distance just the way the surface height changes in a water wave.

Pol바카라 영어로ization is simply the direction in space in which each light wave’s electric field is oriented. Because, keep in mind, unlike a water wave which is confined to the surface of the pond (meaning the water height can only v바카라 영어로y up and down), light waves can travel in any orientation and direction. They don’t need any medium in which to propagate.

What physicist Michael 바카라 영어로 discovered in 1845 is that when some materials (called magneto-optic materials) are placed in a magnetic field, the polarization direction of light waves traveling through them will rotate. The amount of this rotation is directly proportional to the strength of the magnetic field, the distance the light travels inside the material, and the material’s Verdet constant. The Verdet constant is simply a measure of the strength of the magneto-optic effect in that specific material. It is usually determined by measurement.

While most transparent dielectric materials are magneto-optic, the effect is usually very weak. However, there are a few materials that have a large Verdet constant. Typically, these are glasses or crystals containing the element Terbium. In particular, the crystal terbium gallium garnet (TGG) exhibits a strong magneto-optic effect and has low absorption at commonly used wavelengths. It also has various other desirable physical properties and is relatively low cost. That’s why TGG is one of the most commonly used materials for making 바카라 영어로 rotators and Isolators.

What is a 바카라 영어로 Isolator?

There are a variety of photonic components that can be constructed based on the 바카라 영어로 rotator, and the 바카라 영어로 isolator is one of the most useful and widely employed of these. It allows polarized light to pass through unimpeded in one direction but attenuates most light that enters from the opposite direction.

A common use of the 바카라 영어로 isolator is at the output end of a laser or laser amplifier to protect it from back reflected light. Specifically, this is light reflected back towards the laser by other optics in the system, or by the object the laser is illuminating (for example, a reflective piece of metal being welded by an industrial laser). If powerful enough, back reflected light can damage a laser. But even at much lower levels, back reflected light can cause laser operating instability, like noise and power fluctuations.

The operation of 바카라 영어로 isolators is conceptually simple and is illustrated in the drawing. Linearly polarized light (coming in from the left) passes through a polarizer (#1) aligned with its polarization. It enters a 바카라 영어로 rotator which rotates the polarization by 45°. The light passes through another polarizer (#2) aligned with this rotated polarization and then into the optical system and process. This configuration allows virtually all the laser light to pass through the device unattenuated.

Any light returned from the optical system or process first passes through a polarizer (#2) which rejects all polarizations different from the original 바카라 영어로 output. This filtered light then passes through the rotator and undergoes another 45° rotation. This puts its polarization at right angles to its original orientation. This means that it will be rejected by the first polarizing beamsplitter (#1).

Designing and manufacturing practical 바카라 영어로 isolators requires balancing several factors. Key parameters are typically aperture size, wavelength range, transmission (attenuation in the forward direction), and isolation (blocking of returned light). Overall maximum laser power rating and laser-induced damage threshold (LIDT) are also often considerations. And, of course, these are all traded off against cost, and sometimes physical size or weight.

Optimizing for these v바카라 영어로ious p바카라 영어로ameters requires making design choices and tradeoffs in the strength and size of the permanent magnet, the required quality of the magneto-optic material (specifically in terms of absorption, index homogeneity, and birefringence), the types of thin film coatings used, and more.

As a result, 바카라 영어로 isolator manufacturers like Coherent offer a range of different products, each optimized for different tasks. Examples include our compactLow Power Rotators and 바카라 영어로for ne바카라 영어로-IR seed lasers,EURYS Rotators and 바카라 영어로for Ti:Sapphire oscil바카라 영어로tors, andTORNOS Rotators and 바카라 영어로specifically designed to prevent optical feedback in 바카라 영어로sers from 405 nm to 980 nm.

Novel Technology for High-Power 바카라 영어로

TGG has long been the 바카라 영어로 rotator crystal of choice for the 650 – 1100 nm spectral range for several reasons. For example, it can be grown with high purity. It has a high Verdet constant and its symmetric cubic crystal structure and low intrinsic birefringence make it easy to achieve high isolation without the need for sensitive alignment processes. And it is relatively low cost.

However, even the purest TGG eventually encounters performance limits due to its bulk absorption. This absorption causes localized heating within the crystal with performance-limiting consequences. As the output power of industrial 바카라 영어로sers has continued to scale up over the past decades, TGG’s inherent absorption and thermo-optical properties have become increasingly disadvantageous.

Potassium Terbium Fluoride (KTF) is another magneto-optic material with a similar transmission range to TGG, as well as a comparable Verdet constant. Most importantly, it possesses a lower bulk absorption coefficient (eight times lower), thermo-optic coefficient (15 times lower), and stress-optic coefficient than TGG. Together, these allow it to avoid the degradations in isolation performance, beam focus, and beam quality that plague TGG-based 바카라 영어로 isolators when exposed to very high laser power.

Early KTF growth efforts produced boules with bubbles, inclusions, and issues of high scatter. These provided no net improvement in transmission over TGG. But Coherent has pioneered numerous process refinements that now deliver improved yields of high-quality KTF at a reduced cost. This has enabled us to produce a cost-competitive series of 바카라 영어로 isolators intended specifically for high-power lasers – theCoherent Pavos Ultra series– that incorporate this material.

Le바카라 영어로n more aboutCoherent 바카라 영어로 and rotators, andkW-class 바카라 영어로 isolators.