Bandpass Filters ( Laser )

Material: Quartz Crystal Available Manufacturing Wavelength Range: 260nm~1800nm Retardance Accuracy: λ/8, λ/4, λ/2, or arbitrary retardation

Polarized light acquires a fixed phase retardation after passing through a waveplate. By order, waveplates are divided into zero-order and multiple-order types; by retardation, into half-wave and 1/4-wave types. The final phase difference is determined by the source formula =2 nd(ne-no)/λ, where λ is the incident wavelength. At a given wavelength, the final phase is determined by plate thickness.

Waveplates (retardation plates or phase shifters) are made from materials which exhibit birefringence. The velocities of the extraordinary and ordinary rays through the birefringent materials vary inversely with their refractive indices. The difference in velocities gives rise to a phase difference when the two beams recombine. In the case of an incident linearly polarized beam this is given by a=2p*d(ne-no)/l (a-phase difference; d-thickness of waveplate; ne,no-refractive indices of extraordinary and ordinary rays respectively; l-wavelength). At any specific wavelength the phase difference is governed by the thickness of the retarder. The thickness of a half waveplate is such that the phase difference is 1/2-wavelength (true-zero order) or some multiple of 1/2-wavelength [(2n+1)l/2multiple order]. A linearly polarized beam incident on a half waveplate emerges as a linearly polarized beam but rotates 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 in rotating the plane of polarization, electro-optic modulation and as a variable ratio beamsplitter when used in conjunction with a polarization cube. The thickness of the quarter waveplate is such that the phase difference is 1/4 wavelength (l/4,true-zero order) or some multiple of 1/4 wavelength [(2n+1)l/2,multiple order]. If the angle q (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 waveplate and rotates the plane of polarization to a certain angle. Quarter waveplates are used in creating circular polarization from linear or linear polarization from circular, ellipsometry, optical pumping, suppressing unwanted reflection and optical isolation.

Quartz waveplates, also called phase retarders, introduce an additional optical path or phase difference between orthogonal light vibrations. They typically use precisely thick birefringent quartz with the optical axis parallel to the surface. A 1/2 (half-wave) plate rotates linear polarization by any angle, with rotation 2 times the angle between incident polarization and the optical axis; the source wording includes "opposite" for the incident polarization. An axis at 22.5° gives45° clockwise output rotation, while45° gives90°. Combined with a polarizing beamsplitter prism, it is often used in beam combiners requiring polarization conversion. A 1/4 plate delays linear polarization by 1/4 wavelength to convert it to circular polarization, and conversely converts circular to linear. Combined with a polarizing beamsplitter, a 1/4 plate can serve in an isolator. Applications include laser, optical communications, and instruments for beam-combiner polarization conversion, isolators, and circulators.

Standard Wavelength: 266; 355; 532; 632.8; 780; 808; 850; 980; 1064; 1310; 1480; 1550

Zero-order waveplates provide zero-order phase retardation. Compared with multiple-order waveplates, they offer better performance, broader bandwidth and lower sensitivity to temperature and wavelength changes. A cemented zero-order waveplate bonds two multiple-order plates with perpendicular optical axes, so one plate's retardation offsets the other's. Net phase change results from their thickness difference, enabling waveplates for any wavelength and phase difference.