The LightSoft company develops professional optical softwares and provides optical engineering and consultant service to the world.

Currently LightSoft has two optical software products,

GratingMaster® ---for thinfilm/1D and 2D grating design based on RCWA (Rigorous Coupled Wave Analysis);

** Can design wide-angle 1D and 2D Dammann Gratings.

 

DOEMaster® ---for general diffractive optical element design based on latest IFTA (Iterative Fourier Trans  form Algorithm) optimization methd;

** The only software in market which can design wide-angle DOE with total diffraction angle up to 120 degree.

What is Thin-film? and its Applications...

The purpose of any optical thin-film coating is to modify the transmittance and reflectance properties of the substrate material to which they are applied. 
The vast majority of optics used in precision scientific, industrial, biomedical and military applications incorporate thin-film coatings on their surfaces. Most coatings can be broadly classified into one of the following categories:

  •  Antireflection (AR):  Used to suppress unwanted reflections that normally occur at the interface between two different materials, such as air and glass
  • High reflection (HR): Mirror coatings are used to increase the reflectivity of a surface
  • Partial reflection: Beamsplitters transmit a specified percentage of input light and reflect the rest. This is often used at nonzero angles of incidence
  • Polarization: Polarizers separate incident light into orthogonally polarized components, typically transmitting one and reflecting the other
  • Filter: These may perform any of the preceding functions, but on a wavelength-selective basis; for example, transmitting one wavelength and highly reflecting a second

What is Grating or diffraction grating?

In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions, called grating orders. The directions of these beams depend on the spacing of the grating, the incident angle and the wavelength of the light. The wavelength dependency makes the grating act as a dispersive element and so can be commonly used in spectrometers.

Gratings can be either transmissive or reflective for incident light. Gratings can also modulate the phase of the incident light rather than its amplitude, which are called phase diffraction grating.

The efficiency of a grating is defined as how much optical power is distributed in each grating order, and it is also dependent on the polarization of the incident light.

Basically, a diffraction grating performs a Fourier Transform, separating a waveform in the time domain into a number of waveforms in the frequency domain.

lou-grating
diffraction-grating

Grating Manufacturing and Applications

A diffraction grating can be produced by first ruling a master grating, and then replicating this master into a large number of exact copies, called replicas, for cost savings and product consistency.

Master gratings can be manufactured using some of the following technologies:

  • Mechanical ruling
  • Holographic recording from photolithography
  • Ion-etching of holographic master based on low-cost semiconductor technology
  • micro-lithography or nano-imprinting technology

Optical gratings have applications in everywhere due to its sensitivity to wavelength and refractive index, beam splitting and phase modulation function.

  • Laboratory spectroscopy systems, like spectrophotometers
  • Telecommunication active & passive modules, like WDM(wavelength division multiplexer), and fiber Bragg grating filter
  • Colour analysis instruments, such as colorimeter
  • Biomedical devices and Life science products, such as bioanalyzers
  • Analytical chemistry application
  • Lasers, ultrafast and high-energy lasers
  • Space flight instruments and astronomy

What is DOE? and Applications...

DOE means Diffractive Optical Element in optics field. Gratings are also DOEs, which have periodic structures. DOE here is generally referred to non-periodic small diffractive optical element, with total element dimension of millimeters in general.
DOE using a thin micro structure pattern can alter the phase of the light propagated through it, which is also referred to as DPE (Diffractive Phase Element). A properly-designed phase pattern can manipulate the light to almost any desired intensity profile.

DOEs have wide applications in industrial, medical, scientific research fields. Here are some examples,

  1. Laser beam shaping 
    During material processing, like laser cutting, laser drilling, and material ablation. The beam profile of the laser in the working plane is crucial to the quality of the end results. By selectively changing the profile, improvements in the process can be made. Laser beam profile can be shaped from Gaussian to uniform top hat either round or square.

2. Generate geometric patterns, such as lines, circles, squares 
The application of these patterns can be used as viewfinder patterns, three-dimensional (3-D) surface measurements in precisely defined dimensions in a specified plane, and representing rulers or scales.

3. Head-mounted displays (Virtual Reality)
Diffractive optics can play a key role in head mounted displays due to its reduced size and weight, and possible low-cost mass production. Four areas are actively studied to replace conventional refractive or reflective optics: Magnifier optics, combiner optics, head and hand tracking, and optical data interface.

4. Lithography and holographic lighting
Beam homogenization in mask projection systems, structured pupil illumination, homogeneous field illumination for normal and highly tilted plane

5. More applications

  • Eliminate spherical and chromatic aberration in  industrial  and medical diffractive focusing elements
  • Generate customized letters or logos
  • Medical laser treatments and diagnostic instruments, such as tattoo, hair removal.
  • Bar code scanner
  • Random Phase Plate
  • Wave-Front Generators or corrector