Top Notch BBO Crystal Production

BBO crystals are among one of the most versatile nonlinear optical products for regularity conversion applications. They can generate ultraviolet, visible, and near-infrared light from various laser resources, such as Nd: YAG, Ti: sapphire, as well as fiber lasers. BBO crystals have high nonlinear coefficients, a wide transparency range, low group-velocity dispersion, and also a high damages limit. Nevertheless, generating premium BBO crystals requires cautious control of the crystal growth process as well as post-growth therapies.

This write-up will clarify how we produce top quality BBO crystals at our company. We will additionally review some advantages and also obstacles of using BBO crystals for regularity conversion.

What is a BBO crystal?

BBO stands for beta-barium borate (β-BaB2O4), a birefringent crystal with a trigonal framework. It belongs to the 3m point team with 3 principal axes: X, Y, and also Z. The Z-axis is parallel to the optical axis of the crystal and is also called the great axis. The X- and also Y-axes are vertical to the optical axis and are called common axes.

BBO crystals have 2 refractive indices: ne for amazing rays and also no for average rays. The distinction between ne and also no relies on the wavelength of light and the temperature level of the crystal. This distinction triggers stage mismatch in between various light polarization elements when circulating through a BBO crystal. Adjusting the angle between the light beam and the crystal axes can compensate this phase inequality.

BBO crystals have huge nonlinear coefficients that permit effective regularity conversions processes such as second-harmonic generation (SHG), third-harmonic generation (THG), fourth-harmonic generation (FHG), fifth-harmonic generation (5HG), sum-frequency generation (SFG) as well as difference-frequency generation (DFG). These processes involve blending two or even more input beam of lights esenyurt escort with different regularities to produce a result beam with a brand-new frequency.

Exactly how Do We Expand BBO Crystals?

We expand BBO crystals using a changed Czochralski method with a platinum crucible. The raw materials are barium carbonate (BaCO3) as well as boric acid (H3BO3), combined in a stoichiometric proportion of 1:2. The mix is then thawed at about 1100 ℃ 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 turning pole that dips into the thaw surface. The rod is gradually brought up while rotating at a constant rate. This triggers a thin melt layer to strengthen on the seed crystal, creating a cylindrical boule.

The development rate relies on temperature gradient, rotation rate, drawing speed, thaw structure, as well as oxygen stress. We thoroughly monitor these variables throughout the growth process to make certain harmony as well as quality of the boule.

The normal size of our boule has to do with 50 mm in size as well as 100 mm in size. After growing, we harden the boule at regarding 900 ° C for numerous hrs to eliminate interior stress and anxiety and also boost optical homogeneity.

Exactly how Do We Cut and also Polish BBO Crystals?

We reduced our boule right into smaller sized pieces according to consumer specs making use of a diamond blade, or cord saw maker. We then polish these items utilizing ruby powder or slurry on actors iron or copper plates.

The reducing angle relies on the desired phase-matching problem for regularity conversion applications. Phase matching describes matching the phase velocities of various beams associated with nonlinear procedures to ensure that they accumulate constructively over fars away inside the crystal.

Types of phase matching

There are 2 types of phase matching: essential stage matching (CPM) and noncritical stage matching (NCPM). CPM occurs when the input beam circulates along one of the primary axes of the crystal, such as the Z-axis, as well as its polarization is vertical to that axis, such as X- or Y-polarized.

NCPM happens when the input light beam propagates at an angle besides absolutely no or 90 degrees worrying one of the major axes, such as the Z-axis. Its polarization is parallel to that axis, such as Z-polarized.

For CPM, we reduced our items at an angle equal to no or 90 degrees concerning among the principal axes. For NCPM, we cut our items at an angle identified by Snell’s legislation:

ni sin( ɵi) = no sin( ɵo) where ni and no are the refractive indices of the input and outcome media, respectively, and ɵi and also ɵo are the angles of occurrence as well as refraction, respectively.

We polish our items using a fine-grained diamond powder or slurry on an actors iron or copper plate. And use consistent pressure and movement to attain a smooth surface with reduced roughness and high flatness. We also layer our items with anti-reflection coverings to reduce representation losses at the crystal surfaces.

Technical Indicators

The regular dimension of our pieces ranges from 1 mm to 25 mm in diameter or size. The surface area quality is far better than 10-5 scratch-dig according to the MIL-PRF-13830B requirement. The surface flatness is far better than lambda/8 at 633 nm wavelength. The parallelism is far better than 10 arc seconds. The clear aperture is larger than 90% of the main area.

What Are the Advantages of Using BBO Crystals?

BBO crystals have many advantages for regularity conversion applications, such as:

High nonlinear coefficients

BBO crystals have large nonlinear coefficients that enable effective frequency conversion processes with low input power demands. As an example, BBO crystals have a nonlinear coefficient d31 of concerning 2 pm/V for SHG at 1064 nm wavelength, which has to do with 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 near-infrared regions. This enables BBO crystals to be made use of for various laser sources with various wavelengths.

Reduced group-velocity diffusion

BBO crystals have reduced group-velocity dispersion (GVD) that decreases temporal expanding of ultrashort pulses during frequency conversion procedures. For instance, BBO crystals have a GVD parameter β2 of regarding -35 fs ^ 2/mm for SHG at 800 nm wavelength, about 2 orders of magnitude smaller than KDP crystals.

High damage limit

BBO crystals have high damage thresholds that can withstand high top and also typical power without deterioration or damages. For example, BBO crystals have a damages threshold of concerning 10 GW/cm ^ 2 for SHG at 1064 nm wavelength with 10 ns pulse period, about five times greater than KDP crystals.

What Are the Challenges of Using BBO Crystals?

BBO crystals also have some difficulties for frequency conversion applications, such as:

Small approval angle

BBO crystals have a little approval angle that limits the input light beam’s light beam aberration and also mode top quality for reliable regularity conversion. For instance, BBO crystals have an acceptance angle of concerning 0.8 mrad-cm for SHG at 1064 nm wavelength, which has to do with 4 times smaller than that of KDP crystals.

Big angular walk-off

BBO crystals have a huge angular walk-off that causes spatial separation in between different polarization elements of light when propagating via a BBO crystal. This lowers the effective communication size as well as lowers the conversion performance. For instance, BBO crystals have an angular walk-off of about 38 mrad for SHG at 1064 nm wavelength, which is about six times larger than KDP crystals.

Temperature sensitivity

BBO crystals’ temperature sensitivity affects their refractive indices and also phase-matching conditions. This requires temperature stabilization or tuning tools to preserve optimal performance. For example, BBO crystals have a temperature transmission capacity of concerning 55 ° C-cm for SHG at 1064 nm wavelength, regarding three times smaller than KDP crystals.

How Do We Evaluate Our BBO Crystal Products?

We check our BBO crystal items by using numerous approaches, such as:

X-ray diffraction (XRD)

We utilize XRD to measure our boules and pieces’ crystal framework and also alignment. We make certain that our items are pure beta-phase without alpha-phase contamination or twinning problems.

Optical transmission (OT)

We utilize OT to measure the optical passage range of our items over their openness range. We guarantee our items are without absorption bands or scattering losses due to impurities or flaws.

Second harmonic generation (SHG)

We use SHG to determine our items’ nonlinear conversion efficiency and also phase-matching angle for a given input wavelength. We ensure that our items satisfy the specifications for SHG applications.

Third harmonic generation (THG)

We make use of THG to gauge our pieces’ nonlinear conversion performance as well as phase-matching angle for a given input wavelength. We guarantee that our items satisfy the specifications for THG applications.

Optical parametric oscillation (OPO)

We utilize OPO to measure our items’ nonlinear conversion efficiency and also phase-matching angle for a given input wavelength and signal/idler wavelengths. We guarantee that our items meet the specs for OPO applications.

Optical parametric amplification (OPA)

We make use of OPA to gauge our pieces’ nonlinear conversion efficiency and also phase-matching angle for a provided input wavelength and also signal/idler wavelengths. We guarantee that our products fulfill the specs for OPA applications.

Optical parametric chirped-pulse amplification (OPCPA)

We use OPCPA to gauge our pieces’ nonlinear conversion effectiveness and phase-matching angle for a provided input wavelength as well as signal/idler wavelengths. We also determine the enhanced pulses’ temporal pulse shape and also spectral bandwidth. We make certain that our items meet the specs for OPCPA applications.
What Are Some Instances of BBO Crystal Applications?

BBO crystals have many applications in different areas, 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, visible, or near-infrared light from various laser sources. For example, BBO crystals can create 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 also Pockels effect. As an example, BBO crystals can generate terahertz radiation from OR or modulate laser beam of lights with EOM.

Quantum optics

BBO crystals work for quantum optical experiments such as entangled photon pair generation, quantum state tomography, quantum cryptography, and quantum width. As an example, BBO crystals can create polarization-entangled photon pairs from SPDC or carry out quantum disturbance measurements with the Hong-Ou-Mandel effect.