1/2 Wavplates, 1/4 Waveplates Crystal Quartz Waveplates
Introduction for CrystaL Quartz Waveplates
Waveplates are made from materials which exhibit birefringence. The velocities of the extraordinary and ordinary rays through the birefringent material varies inversely with their refractive indices. This difference in velocities gives rise to a phase difference when the two beams recombine. At any specific wavelength the phase difference is governed by the thickness of the retarder - waveplate .
Half (λ/2) Waveplate. A linearly polarized beam incident on a half wave crystal quartz waveplate emerges as a linearly polarized beam but rotated such that its angle to the optical axis is twice that of the incident beam. Therefore, half-waveplates can be used as continuously adjustable polarization rotators.
Half-waveplates are used to rotate the plane of polarization, electro-optic modulation and as a variable ratio beamsplitter when used in conjunction with a polarization cube.
Quarter (λ/4) Waveplate - thin-film compensator. If the angle between the electric field vector of the incident linearly polarized beam and the retarder principal plane of the quarter-waveplate is 45, the emergent beam is circularly polarized. When a quarter waveplate is double passed, i.e. by mirror reflection, it acts as a half waveplates and rotates the plane of polarization to a certain angle. Quarter waveplate are used in creating circular polarization from linear or linear polarization from circular, ellipsometry, optical pumping, suppressing unwanted reflection and optical isolation.
Zero Order waveplates are generally preferred since they are least sensitive to variations in wavelength, angle of incidence and temperature.
Air-spaced crystal quartz waveplates are also available. Its performance is as good as cemented zero-order waveplate. Additionally, the air-spaced construction enables it is suitable for the high power laser application. The damage threshold is more than 500 MW/cm2.
Features
Specifications
| Material | Quartz, schlieren grade |
| Construction | Single plate |
| Retardation | λ/4 or λ/2 |
| Retardation Accuracy | ±λ/300 at 20°C ±1°C |
| Wavefront Distortion | ≤λ/10 at 632.8 nm over the full aperture |
| Clear Aperture | ≥central 90% of diameter |
| Surface Quality | 10-5 scratch-dig |
| Wedge | <0.5 arc sec |
| Diameter Tolerance | +0/-0.25 mm |
| Reflectivity per Surface | Single wavelength: R <0.5% total, or 0.25% per surface Dual wavelength: Ravg <1.5% |
| Thickness | Single wavelength: 1 mm, nominal Dual wavelength: 0.5–4 mm, nominal |
| Cleaning | Non-abrasive method, acetone or isopropyl alcohol on lens tissue recommended, caution: fragile, thin optic |
| Damage Threshold | 2 MW/cm2 CW, 2 J/cm2 with 10 nsec pulses |