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BBO Data Sheet (PDF file) Download Acrobat Reader |
BBO has significant advantages over other materials in terms of laser power handling abilities, temperature stability, and substantial freedom from piezoelectric ringing.1,2 Because it relies on the electro optic effect, switching time — aided by the low capacitance of the Pockels cell — is very fast. The wide transparency range of BBO allows it to be used in diverse applications.3
Electro-optic Pockels cells are used in applications that require fast switching of the polarization direction of a beam of light. These uses include Q-switching of laser cavities, coupling light into and out from regenerative amplifiers, and, when used in conjunction with a pair of polarizers, light intensity modulation. Pockels cells are characterized by fast response, since the Pockels Effect is largely an electronic effect that produces a linear change in refractive index when an electric field is applied, and are much faster in response than devices based on acoustic changes in a material, for example.
Because of crystal symmetry and the desire for the light beam to experience no birefringence in the absence of an electric field, INRAD BBO Pockels cells are transverse-field devices.
The quarter-wave voltage is Vl/4 = ld / (4 r22 no3 l). The quarter-wave voltage is proportional to d/l, the electrode spacing divided by the crystal length, is inversely proportional to the electro-optic coefficient4 r22, and decreases when operated at shorter wavelengths, l.
The standard INRAD BBO Pockels cell, PBC05-DC04, is a single-crystal device with a 3.5 mm aperture and a quarter-wave voltage at 1064 nm of 4.8 kV. Single-pass transmission of the cell at the design wavelength is > 98%.
The compact PBC05 Q-switch housing is 1" in diameter and 2" long. Electrical connection is made by way of miniature banana connectors; mating connectors are provided with each BBO Pockels cell.
A smaller aperture BBO Pockels cell, the PBC05-DC03, has a 2.5 mm aperture with a quarter-wave voltage of 3.4 kV at 1064 nm. Larger aperture devices, with two crystals in series, are offered under our PBC06 series. In addition, custom-designed Q-switches are available.
Piezoelectric ringing in BBO is small, as evidenced by comparison to KD*P and LiNbO3 Pockels cells. Transmission of a test laser beam at 633 nm, with the Pockels cell placed between parallel polarizers, is shown in the following oscilloscope traces. Application of the quarter-wave voltage for each cell caused the transmitted light intensity to decrease to one-half. Operation at the quarter-wave voltage accentuates the appearance of acoustic ringing. In the traces, the 1® indicates ground or zero light intensity. Plots are shown using KD*P, LiNbO3, and BBO as the Pockels cell material.
KD*P
LiNbO3
Clearly, ringing associated with use of BBO is much less than when either KD*P or LiNbO3 is used. The last trace shows the transmission with BBO in the typical double-pass configuration at the quarter-wave voltage, switching at 5 kHz — the maximum rate allowed by the high voltage driver that was used. In this last trace, intensity is a maximum when voltage is applied; the bottom trace was taken with the laser beam blocked.
BBO
BBO
LITERATURE REFERENCES
1. G.D.Goodno, Z.Guo, R.J.D.Miller, I.J.Miller, J.W.Montgomery, S.R.Adhav, and R.S.Adhav, Investigation of b-BaB2O4 as a Q switch for high power applications, Appl. Phys.Lett. 66(13), 1575 (1995).
2. E.Cheung, S.Palese, H.Injeyan, C.Hoefer, J.Ho, R.Hilyard, H.Komine, J.Berg, and W.Bosenberg, High Power Conversion to Mid-IR Using KTP and ZGP OPOs, OSA TOPS Volume 26, page 514, Advanced Solid State Lasers (1999).
3. S.J.Hamlin, R.Wu, L.A.Bosworth, J.A.Hutchinson, L.T.Marshal, and T.Caughey, BBO Electro-optical Q-switch @ 1.54 µm, OSA TOPS Volume 19, page 171, Advanced Solid State Lasers (1998).
4. H.Nakatani, W.Bosenberg, L.K.Cheng, and C.L.Tang, Linear electro-optic effect in barium metaborate, Appl. Phys.Lett. 52(16), 1288 (1988).
| BBO Pockels Cell Specifications | ||||
| M/N | PBC05-DC04/1064 | PBC05-DC03/1064 | PBC06-DC06/1064 | PBC06-DC04/1064 |
| Aperture Diameter | 3.5 mm | 2.5 mm | 5.5 mm | 3.5 mm |
| Number of Crystals | one | two | ||
| Quarter-Wave Voltage @ 1064 nm |
4.8 kV | 3.6 kV | 3.6 kV | 2.4 kV |
| Intrinsic Contrast @ 1064 nm |
> 1000 : 1 | > 500:1 | ||
| Optical Transmission | > 98 % T | > 97 % T | ||
| Damage Threshold* (Nanosecond Pulses) |
> 500 MW / cm2 | |||
| Damage Threshold* (cw Power) |
> 3 kW / cm2 | |||
| Wavefront Distortion @ 1064 nm |
< l / 8 | |||
| Electrical Contacts | two, electrically floating, miniature banana plugs | |||
| Typical Capacitance | 3 pF | 3 pF | 4.5 pF | 5 pF |
| Outline Dimensions | 1" Diameter x 2" Long Cylinder | 1.25" Diameter x 2.7" Long Cylinder | ||
| * Damage Threshold values are for reference only and are not guaranteed. | ||||
Transmission of BBO. Discontinuity at 850nm is an experimental artifact.
Reflectance of standard 1064 nm AR coating on BBO Q-switch.
INRAD offers a line of Pockels Pockels Cell Drivers that are suitable for operating INRAD Q-switches.
The drivers are either of the boxed variety or of the printed circuit board (pcb) type. The boxed variety are powered from line voltage; they have convenient knobs, switches, and connections by which to adjust the driver high voltage level, set the transition time, and access high voltage and timing signals.
| BBO Pockels Cells | ||
| Model | Description | Aperture |
| PBC03-DC516/248 | BBO Pockels Cell, with AR coated windows, dry cell, for 248 nm operation | 5 x 16 mm |
| PBC04-DC710/1064 | BBO Pockels Cell, with AR coated windows, dry cell, for IR nm operation | 7.5 x 10 mm |
| PBC05-DC03/1064 | BBO Pockels Cell, with AR coated windows, dry cell | 2.5 mm |
| PBC05-DC04/1064 | 3.5 mm | |
| PBC06-DC04/1064 | BBO Pockels Cell, dual crystal, with AR coated windows, dry cell | 3.5 mm |
| PBC06-DC06/1064 | 5.5 mm | |
| Note: Custom wavelengths are available. | ||
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