Lasers for holography
Our customers select our ultra-reliable laser sources to support their work across several holographic applications:
Holographic diffraction grating fabrication
Holographic optical element (HOE) fabrication
Embossed holography for security application
Holography research combining several measurement techniques
CW C-DPSS single frequency lasers for holography
Skylark Lasers’ 640 NX and 532 NX are ideal for holographic applications, reaching the highest output powers available on a compact design. Our lasers provide excellent beam quality with a TEM00 mode and an M2 factor < 1.1. The long-term wavelength drift of our lasers is < 1 pm with a peak-to-peak power stability of < 1%.
Customers seeking a solid state replacement for 325 nm and 442 nm HeCd lasers have selected our lasers for their higher output power, higher output stability, and greater coherence.
Ideal laser specifications for holography
The field of holography covers techniques which aim to record and reproduce the wave information of an object. While, traditional photographs store only the amplitude information of an object, holograms also include phase. This allows for a complete wave description. As such, holograms look three-dimensional, when viewed from different angles. Holography has seen uses not only in art and design, but also in security and data storage. Currently, a major effort is focused on using metasurfaces to overcome limitations on bandwidth, field of view and pixel size.
Holograms are created by scattering coherent light of an object, which is then interfered with a reference onto a holographic plate.
The resulting interference pattern is then developed by chemical means. There are two main types of holography, which differ based on the planes of interference in the holographic plate.
Reflection holography, where the interference fringes lie parallel to the plate and transmission, with the fringes being normal. Reflection holograms can be viewed with white light and they are widely used in art exhibitions. Transmission holograms need the original source to be reconstructed again and have found uses as security checks.
There are a few key characteristics that indicate whether a laser is suitable for holography. The imaged object needs to be suitable for your source. In particular, it’s reflectivity should be as high as possible for you source wavelength. Depending on the material, thermal expansion can be an issue as well, along with object smoothness. On the source/setup side of things, it is very much all about stability! Because holography is an interferometric method, it requires high source stability. Vibration and noise can be detrimental to the quality of your holograms, resulting in unwanted artifacts.
The narrow linewidth of the laser is a key characteristic that needs to be considered. Any phase difference between the two light paths will reduce the resolution available in the final image. This is not so critical during the reproduction of holographic plates and the coherence can be much shorter.
Directly correlated to the spectral linewidth, coherence length is important for generating a stable interference pattern. Single frequency lasers can typically produce a coherent light source that is able to produce high resolution holographic images. A longer coherence length allows for more flexibility and complexity in holography setups.
As with standard photography, the creation of a holographic image requires an exposure time, which is dependent on the sensitivity of the recording media and the amount of light that is available. Higher power laser outputs offer shorter exposure times and larger fields of view.
For static objects in a vibration isolated environment, exposure time becomes less critical and lower power lasers can be considered. Instead, wavelength stability becomes critical, as a slight drift or mode-hopping of the wavelength can cause distortion of the final image.
The final consideration when looking at lasers for holography is the wavelength needed for the best results. For example, security labels would be ineffective if they were recorded in the IR region, outside the range of the human eye, and many modern holographic images are created using multiple wavelengths - red, green and blue - in order to produce a coloured final image. Holographic applications that do not rely on the eye can be operated out with the visible spectrum and data storage, for instance, would benefit from shorter UV wavelengths, leading to higher information density.
For more information, check out our guide to choosing the right laser for your holography set up.