BBO crystals are one of one of the most flexible nonlinear optical products for regularity conversion applications. They can produce ultraviolet, visible, and near-infrared light from different laser sources, such as Nd: YAG, Ti: sapphire, and fiber lasers. BBO crystals have high nonlinear coefficients, a wide openness variety, low group-velocity dispersion, and a high damages limit. Nonetheless, creating top notch BBO crystals requires cautious control of the crystal growth process and also post-growth therapies.
This write-up will discuss just how we create high-grade BBO crystals at our business. We will additionally discuss some advantages and also difficulties of using BBO crystals for regularity conversion.
What is a BBO crystal?
BBO represents beta-barium borate (β-BaB2O4), a birefringent crystal with a trigonal framework. It belongs to the 3m point group with 3 principal axes: X, Y, as well as Z. The Z-axis is alongside the optical axis of the crystal as well as is likewise called the wonderful axis. The X- and Y-axes are perpendicular to the optical axis as well as are called common axes.
BBO crystals have 2 refractive indices: ne for remarkable rays as well as no for average rays. The distinction in between ne and also no depends on the wavelength of light and the temperature of the crystal. This difference creates stage mismatch between different light polarization elements when propagating via a BBO crystal. Changing the angle in between the beam and also the crystal axes can compensate this phase mismatch.
BBO crystals have huge nonlinear coefficients that permit efficient frequency conversions processes such as second-harmonic generation (SHG), third-harmonic generation (THG), fourth-harmonic generation (FHG), fifth-harmonic generation (5HG), sum-frequency generation (SFG) and difference-frequency generation (DFG). These procedures involve blending 2 or more input beam of lights with various regularities to generate a result beam with a brand-new regularity.
Exactly how Do We Grow BBO Crystals?
We expand BBO crystals using a modified Czochralski method with a platinum crucible. The raw products are barium carbonate (BaCO3) and boric acid (H3BO3), blended in a stoichiometric proportion of 1:2. The blend is then thawed at regarding 1100 ° C under an oxygen atmosphere.
The seed crystal is a little BBO crystal with a well-defined positioning along among its primary axes. The seed crystal is connected to a rotating rod that dips into the thaw surface area. The rod is slowly brought up while rotating at a constant rate. This creates a slim thaw layer to strengthen on the seed crystal, creating a round boule.
The development price depends upon temperature level gradient, rotation speed, drawing rate, thaw structure, and oxygen pressure. We meticulously check these factors during the development procedure to make certain harmony and also top quality of the boule.
The normal size of our boule has to do with 50 mm in diameter and also 100 mm in length. After expanding, we harden the boule at about 900 ° C for several hrs to soothe internal anxiety as well as enhance optical homogeneity.
How Do We Cut and Gloss BBO Crystals?
We reduced our boule right into smaller items according to consumer specifications making use of a diamond blade, or cord saw device. We then polish these items making use of ruby powder or slurry on actors iron or copper plates.
The reducing angle depends upon the wanted phase-matching condition for frequency conversion applications. Stage matching describes matching the stage speeds of different beam of lights involved in nonlinear procedures to make sure that they add up constructively over cross countries inside the crystal.
There are 2 sorts of phase matching: critical stage matching (CPM) and also noncritical stage matching (NCPM). CPM happens when the input beam of light propagates along one of the primary axes of the crystal, such as the Z-axis, and also its polarization is vertical to that axis, such as X- or Y-polarized. NCPM occurs when the input beam propagates at an angle apart from no or 90 degrees concerning among the primary axes, such as the Z-axis. Its polarization is alongside that axis, such as Z-polarized.
For CPM, we cut our items at an angle equal to absolutely no or 90 levels concerning among the primary axes. For NCPM, we reduced our pieces at an angle identified by Snell’s regulation:
ni sin( ɵi) = no sin( ɵo) where ni and no are the refractive indices of the input and also result media, specifically, and also ɵi and ɵo are the angles of incidence as well as refraction, respectively.
We polish our items utilizing a fine-grained diamond powder or slurry on a cast iron or copper plate. We apply uniform pressure and also motion to achieve a smooth surface area with low roughness as well as high flatness. We also coat our pieces with anti-reflection layers to reduce representation losses at the crystal surfaces.
The typical size of our pieces ranges from 1 mm to 25 mm in size or size. The surface area quality is much better than 10-5 scratch-dig according to the MIL-PRF-13830B requirement. The surface flatness is better than lambda/8 at 633 nm wavelength. The parallelism is much better than 10 arc secs. The clear aperture is larger than 90% of the central area.
What Are the Benefits of Using BBO Crystals?
BBO crystals have numerous benefits for regularity conversion applications, such as:
· High nonlinear coefficients: BBO crystals have large nonlinear coefficients that make it possible for reliable regularity conversion processes with low input power demands. For instance, BBO crystals have a nonlinear coefficient d31 of about 2 pm/V for SHG at 1064 nm wavelength, which is about 10 times larger than KDP crystals.
· Broad transparency range: BBO crystals have a wide openness variety from 189 nm to 3500 nm, covering ultraviolet, visible, and also near-infrared areas. This permits BBO crystals to be utilized for various laser sources with different wavelengths.
· Reduced group-velocity diffusion: BBO crystals have low group-velocity dispersion (GVD) that decreases temporal broadening of ultrashort pulses during regularity conversion procedures. For instance, BBO crystals have a GVD parameter β2 of concerning -35 fs ^ 2/mm for SHG at 800 nm wavelength, regarding two orders of size smaller than KDP crystals.
· High damages threshold: BBO crystals have high damages limits that can withstand high height as well as ordinary power without degradation or damages. For example, BBO crystals have a damages limit of regarding 10 GW/cm ^ 2 for SHG at 1064 nm wavelength with 10 ns pulse duration, concerning 5 times higher than KDP crystals.
What Are the Challenges of Using BBO Crystals?
BBO crystals additionally have some challenges for regularity conversion applications, such as:
· Tiny approval angle: BBO crystals have a tiny approval angle that limits the input beam’s beam aberration and mode quality for efficient regularity conversion. For example, BBO crystals have an approval angle of regarding 0.8 mrad-cm for SHG at 1064 nm wavelength, which has to do with four times smaller sized than that of KDP crystals.
· Big angular walk-off BBO crystals have a huge angular walk-off that causes spatial separation in between various polarization components of light when propagating through a BBO crystal. This minimizes the efficient communication length and reduces the conversion effectiveness. As an example, BBO crystals have an angular walk-off of about 38 mrad for SHG at 1064 nm wavelength, which has to do with six times larger than KDP crystals.
· Temperature level sensitivity: BBO crystals’ temperature level of sensitivity influences their refractive indices and also phase-matching problems. This calls for temperature level stablizing or tuning gadgets to preserve optimal performance. For example, BBO crystals have a temperature bandwidth of concerning 55 ° C-cm for SHG at 1064 nm wavelength, about three times smaller sized than KDP crystals.
Exactly how Do We Evaluate Our BBO Crystal Products?
We examine our BBO crystal items by utilizing different methods, such as:
· X-ray diffraction (XRD): We make use of XRD to gauge our boules and also items’ crystal structure as well as alignment. We make sure that our products are pure beta-phase without alpha-phase contamination or twinning problems.
· Optical transmission (OT): We make use of OT to determine the optical transmittance range of our items over their transparency array. We ensure our products are devoid of absorption bands or scattering losses due to contaminations or problems.
· Second harmonic generation (SHG): We utilize SHG to gauge our items’ nonlinear conversion effectiveness as well as phase-matching angle for an offered input wavelength. We ensure that our items fulfill the specs for SHG applications.
· Third harmonic generation (THG): We use THG to measure our pieces’ nonlinear conversion effectiveness and also phase-matching angle for a given input wavelength. We guarantee that our products meet the requirements for THG applications.
· Optical parametric oscillation (OPO): We use OPO to measure our items’ nonlinear conversion efficiency and phase-matching angle for an offered input wavelength and also signal/idler wavelengths. We ensure that our items fulfill the specifications for OPO applications.
· Optical parametric boosting (OPA): We utilize OPA to determine our items’ nonlinear conversion effectiveness as well as phase-matching angle for a provided input wavelength as well as signal/idler wavelengths. We ensure that our items fulfill the specs for OPA applications.
· Optical parametric chirped-pulse amplification (OPCPA): We utilize OPCPA to measure our pieces’ nonlinear conversion performance and phase-matching angle for an offered input wavelength and also signal/idler wavelengths. We also determine the amplified pulses’ temporal pulse shape as well as spooky data transfer. We ensure that our items satisfy the specifications for OPCPA applications.
What Are Some Examples of BBO Crystal Applications?
BBO crystals have numerous applications in numerous fields, such as:
· Laser scientific research: BBO crystals are commonly used for frequency conversion procedures such as SHG, THG, OPO, OPA, as well as OPCPA to generate ultraviolet, noticeable, or near-infrared light from various laser resources. For instance, BBO crystals can produce 266 nm light from 1064 nm Nd: YAG lasers or 400 nm light from 800 nm Ti: sapphire lasers.
· Nonlinear optics: BBO crystals are likewise utilized for various other nonlinear optical procedures such as sum-frequency generation (SFG), difference-frequency generation (DFG), optical rectification (OR), electro-optic modulation (EOM), and Pockels impact. For instance, BBO crystals can create terahertz radiation from OR or modulate laser light beams with EOM.
· Quantum optics: BBO crystals serve for quantum optical experiments such as knotted photon set generation, quantum state tomography, quantum cryptography, and quantum metrology. For example, BBO crystals can produce polarization-entangled photon sets from SPDC or perform quantum disturbance dimensions with the Hong-Ou-Mandel impact.
Just How Can I Order Your BBO Crystal Products?
You can order our BBO crystal products by contacting us through e-mail or phone. You can additionally visit our internet site to search our directory and request a quote online. We offer affordable costs and quick delivery worldwide. I value your interest in our BBO crystal products!