Lasers for Holography & Imaging
Skylark Lasers offers high-power, single-frequency laser sources with a coherence length exceeding 100 metres. With long-term power and wavelength stability, our compact lasers are ideal for holography and applications that use holographic techniques.
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
Lasers for holography
Skylark Lasers’ 640 NX and 532 NX are ideal for holographic applications, reaching the highest output powers 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%. For holographic applications requiring a UV laser source, our 320 NX and 349 NX offer ultra-stable performance at output powers up to 200 mW. 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.
What is holography?
Rather than an image as recorded by standard photography, a holographic image is a record of the difference in phase and amplitude intensities of the two light paths as they arrive at the recording media. The resulting interference image is meaningless when viewed under a different light source, but when illuminated by the same light source as used for its creation, the original light path is recreated and the object can be seen as if it were still present. Fine detail, dimensions and the 3D nature of the object can be replicated exactly.
Apart from its frequent application in the arts, holography is also extensively used to prevent forgery in currency or documents, due to the difficulty in reproducing these holograms without the original light source. This requirement for highly accurate phase information is what mandates the use of lasers with excellent spatial and temporal coherence.
Ideal laser specifications for holography
Several factors relating to the laser source are critical for ensuring high resolution holographic images and measurements.
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.
2. Coherence length
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.
3. High power
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.
4. Wavelength stability
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.