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DK242 1/4 Meter Double Monochromator article

DK242 1/4meter double monochromator

  • Internal controller connects to any computer via RS232 or IEEE-488. Hands-off control of three slit assemblies and two grating turrets.
  • Scans in both directions and with Constant Spectral Resolution (CSR).
  • Triple-grating turrets allows high efficiency scanning across a broad spectral range.
  • Additive dispersion increases resolution and reduces stray light for Raman and fluorescence studies, subtractive dispersion minimizes broadening of pulse sources.
  • Integrates with SP filter wheel for automatic filter switching.
  • May be factory configured as a monochromator or spectrograph.
The Pioneer: Better Resolution, Stray Light Control

The DK242 is two cascaded monochromators, with the exit slit of the first monochromator functioning as the entrance slit of the second. This instrument may be factory configured to operate  as either an additive or subtractive dispersion double monochromator. In both modes, the two monochromators act as a double filter with the rejection of stray light being nearly the square of the single monochromator value. In the additive dispersion mode, the DK242 is the equivalent of a half-meter monochromator, but permits greater reduction of stray light. The first grating spreads the spectrum over an angular range; the second grating then doubles this dispersion. The result is twice the resolution of a single 1/4-meter monochromator. In subtractive dispersion mode the first monochromator selects a bandpass. The second monochromator then removes the temporal and angular aberrations introduced by the angular spectral dispersion in the first monochromator.
The DK242 offers a unique solution to practical problems in the spectroscopy of pulsed sources. For example, an ordinary monochromator will introduce up to 250 pico second broadening in light pulses that are passed through the monochromator. Operated in the subtractive dispersion mode, the DK242 reduces this broadening to almost zero because the second monochromator equalizes the optical path length of the first.
The DK242 is also a unique solution to the practical problems of Raman spectroscopy because the high stray light rejection of the two monochromators allows observation close to the laser line. SP's unique CSR scanning technology also improves efficiency in the red and near IR while maintaining resolution. (In the CSR mode, the monochromator's change in dispersion with wavelength is compensated by a change in slit widths while bandpass remains constant. Intensity improvement up to 4x can occur).
Equipped with SP's Direct Digital Drive, the DK242 is a complete computer-controlled instrument. The control electronics are internal, calibration is automatic. Any computer can control the DK242 through its RS232 interface with simple commands (shown in all capital letters) to direct the monochromator to GO TO a wavelength, to SCAN between wavelengths at a preset SPEED, to SELECT gratings, or to report its STATUS.


 Feature  Value
 Design:  Double cascaded Czerny-Turner.
Triple-grating turrets standard in each section.
 Focal Length:  240mm each section
 f/#:  3.9 overall
 Reciprocal Dispersion:  1.60nm/mm (additive) --- (with 1200 g/mm grating)
 Wavelength Drive:  Dual worm and wheel with electronic synchronization and computer control. Programmable in additive or subtractive dispersion
 Programmable in additive or subtractive dispersion
 Wavelength Precision:  0.01nm (additive)    0.01nm (subtractive)
 Wavelength Accuracy:  ± 0.30nm standard (with 1200 g/mm grating)
 Scan Speed:  >1 to 1200nm/minute (with grating)
 Stray Light:  < 10-9
 Slits:  Unilateral, computer controlled, curved entrance and straight exit standard.
 Width - 10μm to 3000μm
 Height - 2mm to 20mm
 Pulse Broadening:  200 ps max (additive) 10 fs max (subtractive)
 Max Resolution:  <0.04nm (additive)    0.06nm (subtractive)
 Gratings:  Two to six gratings (68 x 68mm standard, 68 x 84mm optional) must be purchased. See DK Gratings.
 Software:  Demonstration control program and LabView driver included.
 Power:  110 / 120V, 50/60Hz @ 1A standard. 220/230/240V, 50/60Hz @ 0.5A optional.
 Interface:  RS232 standard
 Warranty:  One year
  • DKBS - Bi-lateral slits
  • DKGPIB - IEEE-488 communication interface (internal)
  • DK2400 and Hand-held controllers for local control
  • IR240 - Gold optics
  • DK2PORT - Bifurcated fiber bundle for attaching 2 devices to 1 port.
  • AB300 - Automated 6 position filter wheel
See options and accessories

Spectral Products & CVI Laser