The Laser Line Tunable Filter (LLTF CONTRAST) is a non-dispersive patented (US patent 7557990) optical tunable bandpass filter based on volume Bragg gratings. It combines very high optical density (> OD6), an outstanding out-of-band rejection, and a wideband tuning range across the visible (VIS) and infrared (NIR, SWIR). The LLTF can be customized to cover the entire 400 nm to 2500 nm spectral range with a high spectral resolution.
It can be coupled with a wide variety of broadband sources, such as supercontinuum, to create a tunable laser source. It can also be used as a cleanup filter for spectroscopy applications.
There are numerous possible LLTF configurations whose spectral range and bandwidth can be finely tuned to fit specific needs. The specifications below of several tried-and-tested standard models may serve as a starting point.
| CONTRAST-SR-VIS | CONTRAST-SR-SWIR | CONTRAST-EXT III | CONTRAST-EXT IV | |
|---|---|---|---|---|
| Spectral range | 400-1000 nm | 1000-2300 nm (2500 nm optional) | 400-1700 nm | 400-2300 nm (2500 nm optional) |
| Bandwidth (FWHM) | 1.5 – 2.5 nm | 2.0 – 5.0 nm | 400-1000 nm: 1.5 – 2.5 nm | 1000-1700 nm: 2.0 – 5.0 nm | 400-1000 nm: 1.5 – 2.5 nm | 1000-2300 nm: 2.0 – 5.0 nm |
| Out-of-band rejection | <-60 dB@±40 nm, typically <-30 dB@±10 nm | <-60 dB@±80nm, typically <-30 dB@±20nm | 400-1000 nm: <-60 dB@±40 nm, typically <-30dB@±10 nm | 1000-1700 nm: <-60dB@±80 nm, typically <-30 dB@±20 nm | 400-1000 nm: <-60 dB@±40 nm, typically <-30dB@±10 nm | 1000-2300 nm: <-60dB@±80 nm, typically <-30 dB@±20 nm |
| Peak efficiency | Typically around 65% | Typically around 65% | Typically around 65% | Typically around 65% |
| Optical density (OD) | > OD6 (measured at 1064 nm) | > OD6 (measured at 1064 nm) | > OD6 (measured at 1064 nm) | > OD6 (measured at 1064 nm) |
| Stabilization time/wavelength step | 20 ms < 1 nm; 25 ms / 1 nm; 28 ms / 2 nm; 35 ms / 5 nm; 50 ms / 10 nm | 20 ms < 1 nm; 25 ms / 1 nm; 28 ms / 2 nm; 35 ms / 5 nm; 50 ms / 10 nm | 20 ms < 1 nm; 25 ms / 1 nm; 28 ms / 2 nm; 35 ms / 5 nm; 50 ms / 10 nm | 20 ms < 1 nm; 25 ms / 1 nm; 28 ms / 2 nm; 35 ms / 5 nm; 50 ms / 10 nm |
| Dimensions (L x W x H) | 9 x 6.3 x 6.7 (inches), 23 x 16 x 17 (cm) | 9 x 6.3 x 6.7 (inches), 23 x 16 x 17 (cm) | 9 x 6.3 x 6.7 (inches), 23 x 16 x 17 (cm) | 11.8 x 9.1 x 6.7 (inches), 30 x 23 x 17.4 (cm) |
| Options & Accessories | ||||
| Fibered output | An X-Y-Z translation adjustment allows coupling optimization. FC\APC standard connector (SMA, FC\PC on demand). Both lens and mirror-based models available | An X-Y-Z translation adjustment allows coupling optimization. FC\APC standard connector (SMA, FC\PC on demand). Both lens and mirror-based models available | An X-Y-Z translation adjustment allows coupling optimization. FC\APC standard connector (SMA, FC\PC on demand). Both lens and mirror-based models available | An X-Y-Z translation adjustment allows coupling optimization. FC\APC standard connector (SMA, FC\PC on demand). Both lens and mirror-based models available |
| Harmonic filter | Second harmonic suppression included over the 400-500 nm spectral range | Second harmonic suppression included over the 850-1250 nm spectral range. Additional filter for 500-850 nm harmonic suppression available upon request | Second harmonic suppression included over the 400-850 nm spectral range | Second harmonic suppression included over the 400-850 nm spectral range |
| Alignement kit | In free space configuration (input/output), the alignment kit allows the user to rapidly find the correct alignment. | In free space configuration (input/output), the alignment kit allows the user to rapidly find the correct alignment. | In free space configuration (input/output), the alignment kit allows the user to rapidly find the correct alignment. | In free space configuration (input/output), the alignment kit allows the user to rapidly find the correct alignment. |
| CONTRAST-X | |
| Spectral range | X represents a custom spectral range: up to 5 gratings. |
| Bandwidth (FWHM) | 0.15 – 0.9 nm |
| Out-of-band rejection | Typically -55 dB @± -5 nm |
| Peak efficiency | Typically around 65% |
| Optical density (OD) | Depends on spectral range |
| Stabilization time / wavelength step | 20 ms < 1 nm; 25 ms / 1 nm; 28 ms / 2 nm; 35 ms / 5 nm; 50 ms / 10 nm |
| Dimensions (L x W x H) | 9 x 6.3 x 6.7 (inches), 23 x 16 x 17 (cm) |
| Options & Accessories | |
| Fibered output | An X-Y-Z translation adjustment allows coupling optimization. FC\APC standard connector (SMA, FC\PC on demand). Both lens and mirror based-models available |
| Harmonic filter | Upon request |
| Alignement kit | In free space configuration (input/output), the alignment kit allows the user to rapidly find the correct alignment. |
