electro-optic effect (original) (raw)

Definition: the phenomenon that the refractive index of a material can be modified with an electric field

Alternative terms: electrooptic effect, Pockels effect

Categories: nonlinear optics, physical foundations

• optical effects
  • absorption
  • birefringence
  • diffraction
  • dispersion
  • dispersive waves
  • evanescent waves
  • Faraday effect
  • focusing
  • imaging
  • interference
  • optical aberrations
  • optical phase shifts
  • phase matching
  • photodarkening
  • polarization changes
  • propagation losses
  • reflection
  • refraction
  • scattering
  • spatial walk-off
  • superluminal transmission
  • temporal walk-off
  • thermal blooming
  • thermal radiation
  • total internal reflection
  • wavefront distortions
  • nonlinear optical effects
  • electro-optic effect
    * Pockels effect
  • (more topics)

Related: Pockels effectPockels cellsKerr effectelectro-opticselectro-optic modulatorselectro-optic sampling

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Contents

What is the Electro-optic Effect

The electro-optic effect (or electrooptic effect) is the modification of the optical phase delay (often described with its refractive index) of a medium, caused by an applied electric field. However, some authors more generally consider electro-optic effects such that any optical properties may be affected by an electric field — for example, it may also be a change in absorption characteristics, such as through the Franz–Keldysh effect as used in electroabsorption modulators. In this article, only phase effects are considered.

Pockels Effect

Only non-centrosymmetric materials (mostly nonlinear crystal materials) exhibit the linear electro-optic effect, also called the Pockels effect, where the refractive index change is proportional to the electric field strength (see the article on Pockels effect for more details). This allows for easy and rapid tuning of the refractive index.

Only materials exhibiting the Pockels effect are called electro-optic materials. Some examples of such materials are lithium niobate (LiNbO3), lithium tantalate (LiTaO3), potassium titanyl phosphate (KTP) and β-barium borate (BBO).

Most devices in electro-optics are based on the linear electro-optic effect. It is exploited in Pockels cells, which can be part of electro-optic modulators and electro-optic Q-switches, and for electro-optic sampling.

Kerr Effect

All centrosymmetric media exhibit only the Kerr electro-optic effect, also called Kerr effect, where the refractive index change is proportional to the square of the electric field strength. Although that also allows rapid tuning of the refractive index, this effect is typically much weaker than for the linear effect within the range of electric field strength which the material can tolerate. However, there are special cases where a giant quadratic electro-optic effect is observed [1].

Frequently Asked Questions

What is the electro-optic effect?

The electro-optic effect is the change in a material's refractive index, and thus the optical phase delay, caused by an applied electric field.

What is the difference between the Pockels effect and the Kerr effect?

The Pockels effect is a linear effect where the refractive index change is proportional to the applied electric field strength. The Kerr effect is a quadratic effect where the change is proportional to the square of the field strength.

Which materials exhibit the Pockels effect?

The Pockels effect occurs only in non-centrosymmetric materials, mostly nonlinear crystals. Examples include lithium niobate (LiNbO3), lithium tantalate (LiTaO3), KTP, and BBO.

Which electro-optic effect is stronger?

The Pockels effect is typically much stronger than the Kerr effect within the electric field strengths that materials can tolerate. For this reason, most electro-optic devices are based on the Pockels effect.

Suppliers

Sponsored content: The RP Photonics Buyer's Guide contains 48 suppliers for electro-optic modulators. Among them:

⚙ hardware

Raicol Crystals offers electro-optic modulators based on RTP (with a temperature compensating design) or BBO.

Besides, we can supply super-polished LBO crystals which can be used as the center piece of an electro-optic modulator. With its high resistance to laser-induced damage, LBO is very suitable for high-power applications, and its transparency range is large (160 nm — 2600 nm). We offer highly homogeneous crystals with up to 100 × 100 mm2 and very low bulk absorption.

⚙ hardware

With the introduction of the OM6N series of high-speed optical modulators, Thorlabs has designed and manufactured a new all-reflective technology based on deformable mirrors for modulating laser power in the 700 — 1350 nm range. This Pockels cell or AOM alternative introduces nearly zero dispersion to ultrafast laser pulses. This solution extends Thorlabs’ existing collection of adaptive optics and EO modulators.

⚙ hardware

Electro-optic crystals like LiNbO3, LiTaO3, DKDP, BBO, KTP and RTP crystals in conjunction with HF drivers are available for phase or amplitude modulation. ALPHALAS has a large stock of Pockels cells and phase modulators for most of the standard laser wavelengths.

⚙ hardware🧩 accessories and parts🧴 consumables🔧 maintenance, repair📏 metrology, calibration, testing💡 consulting🧰 development

Hangzhou Shalom EO offers Pockels cells and based on DKDP, BBO, LiNbO3, and MgO:LiNbO3 crystals. Shalom EO’s Pockels cells, available in stock and custom versions, deliver the competitive edges of excellent optical transmission at your wavelengths of interest, low half-wave voltage, high damage threshold, and low insertion loss for ideal applications like pulse picking and laser cavity dumping. Various standard and custom extinction ratios are available. Recently, we have succeeded in developing a 3-pin connector DKDP Pockels cells for 755 nm alexandrite lasers manufactured using 1 pce of 99% deuteration DKDP crystal with 3 gold plating.

In addition, Shalom EO also provides off-the-shelf and custom electro-optic crystals for EO modulation. The crystals feature rich dimension/orientation options, and large apertures, while also boasting high-precision polishing and different kinds of coatings. Cr–Au electrodes can be deposited. Various substrate materials are available: DKDP, BBO, LiNbO3, MgO:LiNbO3, TeO2, and HGTR-KTP crystals. EO modulation crystals could be offered in the forms of crystal boules, crystal blanks, and crystals with AR coatings and electrodes.

⚙ hardware

GWU's portfolio of electro-optical devices can meet even demanding requirements. The BBO or KD*P Pockels cells offer a high extinction ratio, fast switching capability and a high damage threshold. They can be configured in flexible design, either free-space or fiber-coupled. We also offer driver electronics.

Bibliography

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