The SHR is an ideal low-cost high-precision spectrometer for measuring laser wavelength in a large field of laser applications, as well as in the process of alignment and testing of solid-state lasers, diode lasers, dye lasers and OPOs.
The SHR optical scheme is based on an Echelle diffraction grating operating in high spectrum orders and a linear image sensor used as a detector. The SHR does not contain any moving elements; powering and control are performed from a computer via the Full-Speed USB interface. The SHR can be triggered from your laser source via standard TTL-level signals.
Laser beam is steered to the SHR entrance slit either via a multimode optical fiber fitted with a diffuse attenuator (both are included in the delivery set) or directly, without any fibers.
Diffuse attenuator FA-3. Contains two diffuse quartz glasses and SMA-905 connector. Axial adjustment of the fiber end relative to diffusive elements
The SHR allows quick and easy measuring of absolute wavelength value of both CW and pulsed lasers with outstanding precision of ± 3 pm within a widest spectral range of 190-1100 nm, as well as detecting FWHM of the analysed line.
Apart from wavelength measuring the SHR provides demonstration of analysed spectra with resolution of 30000 (λ/Δλ<FWHM) which constitutes from 6pm for the UV spectrum range to 40pm for the NIR. The SHR also ensures on-line monitoring of the above values and spectra in the process of tuning the analysed wavelength.
The software for the SHR, WLMeter, features a possibility to check the accuracy and correct it, if necessary, with any known wavelength guided to the SHR: the laser with known wavelength (for example, any He-Ne laser with wavelength of 632.816 nm) or any spectral line with certain constant wavelength value).
WLMeter features another useful function “Lines Array” for monitoring and saving the central wavelength value during time.
In respect of wavelength resolution and accuracy the SHR is an alternative to a long-focus monochromator (focal length of more than 1000mm), equipped with an appropriate CCD. But unlike the monochromator, the SHR has no moving parts and provides real-time measurements without scanning of diffraction grating. The SHR is rigid, stable and accurate, ensures absolute reliability and has more reasonable price.
The SHR wavelength meter is not directly intended for analysis of plasma emission and other populated spectra (refer to the SPECIFICATIONS, line “Source linewidth requirement”). However, the SHR can be applied in analysis of narrow spectral intervals within the spectral width of the Echelle order – from 0.5 nm in the UV spectrum range (190 nm) to 18nm in the IR (1200 nm), preliminarily separated with a filter or a monochromator. The High-Aperture Short-Focus monochromator ML44 can be used for this purpose.
|Operation modes||CW and pulsed (externally triggered)|
|Spectral range, nm||190 — 1100|
|Absolute accuracy, pm||± 3|
|Spectral resolution (instrument function, λ/ΔλFWHM)||30 000 (from 6pm at 193nm to 40pm at 1200nm, refer to Fig.1)|
|Source linewidth requirement, cm-1||≤125 (from 0.5nm at 193nm to 18nm at 1200nm, refer to Fig.2)|
|Sensitivity||less than 0.5 µW at 632.8nm for min exposure time of 7ms|
|Optical interface||-optical fiber 400µm dia, 1000mm length, connector SMA-905|
|-diffuse attenuator FA-3 equipped with SMA-905|
|Requirements to external trigger pulse (for pulsed lasers)|
|— amplitude, V||3-15|
|— pulse duration FWHM, µs||5-20|
|— rise time, µs||~10|
|Computer interface||Full Speed USB|
|Dimensions, mm||165 * 215 * 90|
Below you can see graphs showing how spectral resolution and maximum analyzed spectral line width depend on the wavelength of analyzed radiation for SHR.
You can fully trust the results of FWHM measurement because the SHR will tell you if FWHM of analyzed line is less than the instrument function. Take for example Nd:YAG laser in two operation modes: free running mode and Q-switched mode. In the free running mode (refer to Figure 5) width of 1064nm line is less than 40pm, and the SHR tells it cannot resolve its FWHM (refer to the “Spectra” paragraph). In the Q-switched mode (refer to Figure 6), the line is wide and can be precisely measured with the SHR.
Below you can carry out the estimated values calculation for spectral resolution and source linewidth requirement depending on wavelength of the analyzed light.