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Littrow Prisms
Littrow Prisms: Precision Beam Folding and Wavelength Selection
Littrow prisms are specialized optical elements that play a key role in beam steering, wavelength dispersion, and external cavity laser tuning. Their unique geometry allows for compact optical path folding and precise wavelength control, making them valuable in spectroscopic systems, tunable lasers, and monochromators.
Named after the German physicist Otto von Littrow, these prisms are typically right-angled isosceles prisms, optimized so that light entering at a specific angle is retroreflected along the same path, either directly or after a controlled internal reflection. When used with diffraction gratings in a Littrow configuration, they become powerful tools for wavelength selection and laser feedback.
How Littrow Prisms Work
A Littrow prism has a 30°-60°-90° geometry, and is often used such that light enters one face at the Brewster angle and reflects internally off the hypotenuse. The geometry ensures that the reflected beam exits in the same direction it entered, creating a folded optical path. This design minimizes space requirements in complex optical systems and maintains beam alignment.
In laser cavities, especially tunable external cavity diode lasers (ECDLs), Littrow prisms can work in conjunction with a diffraction grating to reflect only a specific wavelength back into the laser cavity, enabling single-mode operation or narrow linewidth control.
Key advantages include:
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Efficient Retroreflection: Minimizes optical path deviation while folding the beam path.
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Compact System Design: Allows for tight integration in space-limited environments.
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High Spectral Selectivity: When used with a grating, enables precise wavelength feedback.
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Reduced Losses at Brewster Angle: Optimized for low reflectance and high transmission.
Applications of Littrow Prisms
Littrow prisms are used across several advanced optical applications, particularly where precision wavelength control or beam folding is needed:
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Tunable Laser Systems: Littrow prisms are key components in external cavity setups, where they reflect only the desired wavelength back into the laser diode, stabilizing and tuning the output.
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Spectroscopy and Monochromators: They are used to steer and select specific wavelengths of light for high-resolution spectral analysis.
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Beam Steering in Optical Setups: Due to their retroreflective behavior, Littrow prisms are ideal for folding beam paths in compact laboratory instruments or optical benches.
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Fiber Optic Communication: In systems requiring precise channel selection or tuning, Littrow prisms contribute to wavelength stabilization and filtering.
Choosing the Right Littrow Prism
When selecting a Littrow prism, consider the optical material (typically BK7 or fused silica), angular precision, coating type (AR-coated for specific wavelengths), and compatibility with your laser wavelength range. For high-power or UV applications, fused silica may be preferred due to its superior transmission and damage threshold.
At FindLight, we feature a diverse range of Littrow prisms engineered for performance and reliability. Whether you’re building a tunable laser source or designing a compact spectroscopic instrument, our product listings include technical details and supplier info to help streamline your selection process.
Explore Littrow Prisms on FindLight
Need precise wavelength control or space-saving beam folding? Explore our selection of Littrow prisms and request quotes directly from leading suppliers, only on FindLight.
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