A blazed grating – also called echelette grating (from French échelle = ladder) – is a special type of diffraction grating. It is optimized to achieve maximum grating efficiency in a given diffraction order. For this purpose, maximum optical power is concentrated in the desired diffraction order while the residual power in the other orders (particularly the zeroth) is minimized. Since this condition can only exactly be achieved for one wavelength, it is specified for which blaze wavelength the grating is optimized (or blazed). The direction in which maximum efficiency is achieved is called the blaze angle and is the third crucial characteristic of a blazed grating directly depending on blaze wavelength and diffraction order.

Strehlformula

For the Littrow configuration, this becomes 2 d sin ⁡ θ B = m λ {\displaystyle 2d\sin {\theta _{B}}=m\lambda } . By solving for θ B {\displaystyle \theta _{B}} the blaze angle can be calculated for arbitrary combinations of diffraction order, wavelength and line spacing:

Like every optical grating, a blazed grating has a constant line spacing d {\displaystyle d} , determining the magnitude of the wavelength splitting caused by the grating. The grating lines possess a triangular, sawtooth-shaped cross section, forming a step structure. The steps are tilted at the so-called blaze angle θ B {\displaystyle \theta _{B}} with respect to the grating surface. Accordingly, the angle between step normal and grating normal is θ B {\displaystyle \theta _{B}} .

Strehlratio MTF

The blaze angle is optimized to maximize efficiency for the wavelength of the used light. Descriptively, this means θ B {\displaystyle \theta _{B}} is chosen such that the beam diffracted at the grating and the beam reflected at the steps are both deflected into the same direction. Commonly blazed gratings are manufactured in the so-called Littrow configuration.

Inge was born on December 20, 1934 in Baden Austria to her late parents Michael Stenzenberger & Hermine Stenzenberger (nee Witt). Growing up, Inge enjoyed the outdoors, hiking & mountain climbing. She became a nurse practicing medicine in Austria, England, Toronto & Cobourg. Inge remained in Cobourg until her retirement from nursing after her dedication to the medical field for over 40 years. After retirement, Inge found happiness in gardening, flowers, plants & travelling with her family. Inge always took pride in staying active and healthy. She enjoyed going to Curves & was one of the oldest members.

Strehlpronunciation

A special form of a blazed grating is the echelle grating. It is characterized by particularly large blaze angle (>45°). Therefore, the light hits the short legs of the triangular grating lines instead of the long legs. Echelle gratings are mostly manufactured with larger line spacing but are optimized for higher diffraction orders.

Strehlratio calculator

Blazed gratings can also be realized as transmission gratings. In this case the blaze angle is chosen such that the angle of the desired diffraction order coincides with the angle of the beam refracted at the grating material.[2]

Echelle gratings are useful in planet-finding astronomy, and are used on the successful HARPS and PARAS (PRL Advanced Radial-velocity All-sky Search) spectrograph.

What is a goodStrehlratio

The Littrow configuration is a special geometry in which the blaze angle is chosen such that diffraction angle and incidence angle are identical.[1] For a reflection grating, this means that the diffracted beam is back-reflected into the direction of the incident beam (blue beam in picture). The beams are perpendicular to the step and therefore parallel to the step normal. Hence it holds in Littrow configuration α = β = θ B {\displaystyle \alpha =\beta =\theta _{B}} . All other geometries yield anamorphic Littrow expansion or compression of the beam.

Strehlratio formula

Diffraction angles at the grating are not influenced by the step structure. They are determined by the line spacing and can be calculated according to the in-plane version of the grating equation:

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As per Inge’s wishes, cremation has taken place and a Celebration of Life will be held on Friday October 11th, 2024 between the hours of 11AM to 3PM at 12062 2nd Line Road, Roseneath Ontario.

Passed away peacefully at her home in her sleep. Inge is now at rest with her Late husband Erwin Strehl (Predeceased 2020). She leaves behind her devoted son Dieter Strehl.