Diffractive Optics is a discipline in Physics, whose main focus is utilizing the wave nature of light and its qualities to achieve complex optical functions that enable light shaping.
Diffractive optical elements (DOEs) are a family of optics that function by using diffractive optics effects to shape the light beam that is propagated through them into almost any desired intensity profile and shape.
Diffractive Optics design and manufacturing
A diffractive optical element design starts by creating a digital pattern that is then being transcribed, typically by lithography and etching processes, onto an optical window to create micro-patterns on the component. These micro-patterns slow down the light in some areas, while enabling faster passage of the light in others, thus generating a diffraction pattern which if designed correctly, can be perfectly controlled and has absolute angular accuracy.
The design process for diffractive optics is often based on an Iterative Fourier Transform Algorithm (IFTA) aimed at achieving optimal output performance, where optimal is typically defined by the desired optical function including shape, homogeneity, efficiency and spot edges steepness.
To attain these optimal performance, the designer needs to take into account many variables including production and process tolerances as well as performance tolerances, and so the manufacturer’s experience and expertise are of high importance in securing a desired outcome. Holo/Or, being the first to offer Diffractive Optics as a solution to commercial applications over 30 years ago, has a clear advantage in this aspect with its inhouse IP design tools and manufacturing facilities enabling custom solutions per customer’s requirements.
Applications of Diffractive Optics in the industry
A Diffractive Optical Element, sometimes referred to as a diffractive optical lens, is designed to operate on a narrow wavelength band and is therefore rarely used in non-laser based systems. Laser systems manufacturers use diffractive optics lenses in various fields of applications including:
- Material processing applications such as:
- Metal cutting or drilling;
- Laser Filamentation glass cutting;
- Welding and soldering;
- Ablation;
- Laser lift-off; and more.
- Medical and aesthetic medical devices such as:
- Surgical lasers (combining the aiming beam focus with the surgery beam);
- Fractional treatments;
- Body contouring;
- Tattoo and hair removal; and more.
- Microscopy, measurement and analytical instruments;
- 3D sensing with structured light;
- Military applications;
And more.
Optical functions performed by DOEs
The chief optical functions that diffractive optics enable include:
- Beam splitting – a diffractive beam splitter splits an incident beam into any desired number of spots while maintaining the original spot’s characteristics and perfectly controlling the separations between the spots. Diffractive beam splitters can be in either 1 dimensional array, 2 dimensional array or any other desired arrangement including pseudo-random pattern.
- Beam shaping – a diffractive beam shaper modifies the beam into a desired geometrical or freeform shape with a flat-top intensity profile. It generates a uniform energy distribution in the far field or on the work plane, design dependent.
- Beam foci shaping – a diffractive beam foci element manipulates the beam in the propagation axis. A common example is the Elongated Focus DOE which “stretches” the beam waist when going through clear materials.
All these optical functions can be easily realized using a single passive, flat and compact window-like component with diffractive optics. Attempting to achieve this functionality by refractive optics that only use the particle-like nature of light is either flat-out impossible, or often requires costly and bulky multiple optical components, opto-mechanical modules and subsystems. With diffractive optics there is also the option to combine multiple functions on a single DOE element, making it an even more powerful solution where complex functionalities are required.
Due to all of the aforementioned advantages, Diffractive optics is often the go-to solution in many laser applications, especially those demanding a robust and compact solution with high accuracy that is suitable for high-power systems, with Holo/Or being the go-to manufacturer for such elements, especially for high power laser applications.
