Holo/Or, an Israeli based company established in 1989, is the world leader Diffractive Optical Elements manufacturer.
A diffractive optical element (DOE) alters the phase of the light propagated through it by using micro structure patterns fabricated onto the substrate material used for the DOE, typically pure Fused Silica or Zinc Selenide for high-power applications, Polymer on Glass for medium-power applications or plastic for low-power applications. While DOE are often called diffractive lenses in general, this expression refers to a specific family of DOE , i.e Fresnel Zone Plates, while “DOE” refers to all diffractive components, including beam splitters, shapers and focal elements.
The diffractive optical element design can control the phase of the beam and manipulate it into almost any desired intensity profile and shape. Their flexible shaping possibilities, along with other advantages such as their perfect angular accuracy per design wavelength, their high precision and small dimensions, make diffractive optical elements the go-to solution in many laser applications.
With over 30 years of experience, Holo/Or has gained substantial experience and expertise in digital diffractive optics design, and accumulated know-how in diffractive lens design for various applications and industries, providing us with the ability to offer the best diffractive lenses solutions to our customers.
Diffractive optical elements typical designs
One typical diffractive optical element design is a laser beam shaper. There are 2 main types of diffractive laser beam shapers:
- Analytical beam shaper, also known as top-hat beam shaper or flat-top beam shaper, and
- Diffractive homogenizer, also known as diffractive diffuser.
The analytical flat-top beam shaper, is a diffractive optical element designed to modify a highly coherent Gaussian incident beam (typically with M^2 < 1.5) into an output beam with a well defined spot shape with uniform intensity within the spot, and very sharp decay of the energy to nearly zero outside the desired spot area. Typical spot shapes achievable with the top-hat beam shaper include:
- Ring / Circle
The other type of beam shaper, i.e. the diffractive homogenizer, is a diffractive optical element designed to provide a homogenous spot at any desired shape from a non-coherent laser beam with high M^2. Typical output spot shapes include all the above shapes as well as any defined free-form shape desired by the customer.
Another typical diffractive optical element design is the diffractive beam splitter, also known as multispot. The multispot diffractive optical element splits an incident laser beam into multiple channels with predefined arrangement and separations between the spots, and controlled intensity distribution between them.
Diffractive Optical elements design methods
Holo/Or’s DOEs are designed using an in-house developed tool enabling design optimization using the Iterative Fourier Transform Analysis (IFTA), also known as the Gerchberg-Saxton algorithm. Using our unique IFTA merit functions, optimized over many years for multiple applications, Holo/Or can design DOE phases that provide the best diffractive efficiency and uniformity.
The designed pattern is then transcribed into a digital file for lithographic manufacturing process of the elements. In this process, the pattern is written using direct write laser lithography and then dry etched in ICP/RIE plasma etching, to provide a monolithic element with excellent laser damage threshold (LDT) that is almost the same as that of the unpatterned optical substrate.
Our in-house production enables design-for-production that takes tolerances into account, allowing Holo/Or to simulate the performance of elements as they will be in reality, rather than just nominal performance. This enables Holo/Or to give accurate specs that reflect real production tolerances, without the need for prototype production, making custom elements NRE costs competitive compared to other diffractive manufacturers.
Holo/Or can manufacture diffractive optics on wafers up to 150 mm, including in-house dicing to dimensions as small as 2X2mm, as well as working on batches of smaller elements such as 1’’ diameter windows . In addition to our high power monolithic elements, Holo/Or can produce on various substrates depending on system wavelength, power level and required volumes for production, including polymer on glass and plastic elements.
TL; DR - Q & A
Q: What is a diffractive optical element?
A: A diffractive optical element is an optical component that uses micro structures fabricated onto it to alter the phase of the light to achieve almost any desired intensity profile and spot shape.
Q: What are typical diffractive optical elements designs?
A: Typical diffractive optics designs include beam shaping elements such as top-hat / flat-top designs, diffractive homogenizer and diffractive beam splitter / multispot.
Q: What is the production process of a diffractive optical element?
A: Holo/Or’s diffractive optical elements are designed-for-production and optimized for best performance using our unique in-house developed software tools, taking production tolerances into account and providing real performance simulations of the element. They are then fabricated in a lithographic manufacturing process similar to that of semiconductors to achieve maximal accuracy.