Del Mar Photonics - Newsletter December 2010 - Newsletter April 2011
Terahertz THz crystals
Del Mar Photonics supply variety of crystals for THz generation, including ZnTe, GaP, GaSe, LiNbO3 and others.
Below are just few examples of the standard and custom products. Visit our online store to place your order or contact us for custom inquiry today.
THz generation occurs via optical rectification in a <110> ZnTe. Optical rectification is a difference frequency mixing and occurs in media with large second order susceptibility, c(2). Optical rectification is actually analogous to frequency doubling. That is, a polarization is induced in the crystal that is the difference of the individual frequencies instead of their sum. This is due to the well known trigonometric relation: cos(A) * cos(B) = [cos(A+B) + cos(A-B)] / 2. Thus, light of a given frequency passing through a nonlinear medium will generate the same amount of both sum and difference frequencies, corresponding to second harmonic and dc. Another way of describing these processes is to consider the polarization induced in a medium at frequency 2w when it is driven at frequency w:
|P(2w) = c(2w; w, +w) E(w)E(w)||Frequency doubling|
|P(WTHz) = c(W THz; w, - w) E(w)E(w)||Optical Rectification|
For ultrashort laser pulses that have large bandwidth the frequency components are differenced with each other to produce bandwidth from 0 to several THz. Using either way to describe the process, the generated pulse is the envelope of the optical pulse.
Detection of the THz pulse occurs via free-space electro-optic detection in another <110> oriented ZnTe crystal. The THz pulse and the visible pulse are propagated collinearly through the ZnTe crystal. The THz pulse induces a birefringence in ZnTe crystal which is read out by a linearly polarized visible pulse. When both the visible pulse and the THz pulse are in the crystal at the same time, the visible polarization will be rotated by the THz pulse. Using a l/4 waveplate and a beamsplitting polarizer together with a set of balanced photodiodes, we "map" the THz pulse amplitude by monitoring the visible pulse polarization rotation after the ZnTe crystal at a variety of delay times with respect to the THz pulse.
The ability to read out the full electric field, both amplitude and delay, is one of the attractive features of time-domain THz spectroscopy. Note, the visible and THz pulses are collinearly propagated through the ZnTe crystal even though in the figure they appear to be propagate at an angle.
GaP Gallium Phosphite crystals for Terahertz THz applications request a quote - buy standard GaP crystals from online store
GaP crystal part number GaP_10_10_0.002_3 - request a quote
GaP <110> crystal with a thickness of 200μm stuck
(optically contacted) on one GaP <100> with a thickness of 3mm
Aperture, mm 10 x 10 +/-0.1
Thickness of each component, mm 0.002 and 3 +/-10%
Orientation 110 -- 110
Surface quality, scr-dig 40-20 -- 40-20
Flatness, waves at 633 nm - 1
Parallelism, arc min < 3
Certificate of confirmity (actual)
Selenide (GaSe) non-linear crystal for THz generation
Request a quote or
buy from online store
GaSe has wide transparency range, large non-linear coefficient and high damage threshold
LiNbO3 and MgO:LiNbO3 for THz generation Request a quote - Buy from online store
Customer wrote: We want to generate THz wave in these crystals with
femtosecond amplified laser beam @ 800nm.
We need to pump the crystal with tilted IR pulse to generate a THz beam in the orthogonal direction of the end side.
The following crystals are used:
Stoichiometric MgO(0.6%):LiNBO3 Y-cut 5 x 5 x 9.81 mm
5 x 5 mm^2 laser grade polished, with the end side cut at
63° and AR coating at 800nm on the both sides.
Material: Stoichiometric MgO(0.6%):LiNBO3
Dimensions: 5 mm x 5 mm x 9.81 mm
Coating: AR coating at 800nm on the both sides
Part number: MgO(0.6%): LiNbO3_5_5_9.83 - request a quote
sample certificate of conformity
Del Mar Photonics, Inc.
4119 Twilight Ridge
San Diego, CA 92130
tel: (858) 876-3133
fax: (858) 630-2376