Raman charge-coupled device

Major technological and scientific innovation in the past 10 to 15 years has significantly broadened the applicability of Raman spectroscopy, particularly in chemical analysis. Fourier transform (FT)-Raman, charge-coupled device (CCD) detectors, compact spectrographs, effective laser rejection filters, near-infrared lasers, and small computers have contributed to a revolution in Raman instrumentation and made routine analytical applications possible. An increase in instrumental sensitivity by factors as large as 10, plus decreases in both interferences and noise resulted from this revolution. The number of vendors of Raman spectrometers increased from 3 to 12 over a 10-year period, and integrated commercial spectrometers led to turnkey operation and robust reliability. 

Alarie J.P., Stokes D.L., Sutherland W.S., Edwards A.C., Vo-Dinh T., Intensified charge coupled device-based fiberoptic monitor for rapid remote surface-enhanced Raman-scattering sensing, Appl. Spectrosc. 1992 46 1608-1612. 

Similar work was performed by Shaw et al.3 in 1999 when they used FT-Raman, equipped with a charge coupled device (CCD) detector (for rapid measurements) as an on-line monitor for the yeast biotransformation of glucose to ethanol. An ATR (attenuated total reflectance) cell was used to interface the instrument to the fermentation tank. An Nd YAG laser (1064 nm) was used to lower fluorescence interference and a holographic notch filter was employed to reduce Rayleigh scatter interference. Various chemometric approaches were explored and are explained in detail in their paper. The solution was pumped continuously through a bypass, used as a window in which measurements were taken. 

Finally, the introduction of new detectors, such as diode arrays and charge-coupled devices (CCDs), has been a boon for Raman spectroscopy. CCDs permit the accumulation of light in the manner of photographic film additionally, their noise level is lower than that of the photomultiplier tube. In addition, by combining CCDs or diode arrays with optical dispersive elements, entire spectra mav be collected in fractions of a second. 

The charge-coupled device was first used in Raman spectroscopic applications in the late 1980s [45, 46], followed rapidly by the introduction of holographic notch filters [47]. This combination, coupled with the visibility of FT-Raman instruments introduced at around the same time, helped drive the growth of Raman outside the academic lab. Although the throughput advantage of... 

A final consideration for the selection of excitation wavelength in Raman spectroscopy is the efficiency of the silicon-cased charge-coupled device (CCD) detector. Due to silicon absorption, CCD detectors are prohibitively inefficient above 1000 nm. As a result, 785 nm or, more recently, 830 nm are often chosen as the excitation wavelength to fully exploit the diagnostic window while retaining an acceptable quantum efficiency detector. 

Wang Y, Mccreery RL. Evaluation of a diode-laser charge coupled device spectrometer for near-infrared Raman spectroscopy. Analytical Chemistry 1989, 61, 2647-2651. 

CARS CAT CCD CIF CPMD CT CTAB CW Coherent Anti-Stokes Raman Scattering Computerized Axial Tomography Charge-Coupled Device Chemical Image Fusion Carr-Parrinello Molecular Dynamics Computed Tomography Cetyltrimethylammonium Bromide Continuous Wave (Laser)... 

Figure 3.40 shows the layout of a typical Raman analyzer that uses fiber optics for process application. In a Raman process system, light is filtered and delivered to the sample via excitation fiber. Raman-scattered light is collected by collection fibers in the fiber-optic probe, filtered, and sent to the spectrometer via return fiber-optical cables. A charge-coupled device (CCD) camera detects the signal and provides the Raman spectrum. To take advantage of low-noise CCD cameras and to minimize fluorescence interference, NIR diode lasers are used in process instruments. 

In recent years, charge-coupled devices (CCDs) have been used increasingly in Raman spectroscopy (13, 14). A CCD is a silicon-based semiconductor arranged as an array of photosensitive elements, each one of which generates photoelectrons and stores them as a small charge. An example format of a 512 x 512 array is shown in Fig. 2-12. Charges are stored on each individual... 

Figure 6 Block diagram of the two-color optical parametric amplifier (OPA) and IR-Raman apparatus. CPA = Chirped pulse amplification system Fs OSC = femtosecond Ti sapphire oscillator Stretch = pulse stretcher Regen = regenerative pulse amplifier SHGYAG = intracavity frequency-doubled Q-switched Nd YAG laser YAG = diode-pumped, single longitudinal mode, Q-switched Nd YAG laser KTA = potassium titanyl arsenate crystals BBO = /J-barium borate crystal PMT = photomultiplier tube HNF = holographic notch filter IF = narrow-band interference filter CCD = charge-coupled device optical array detector. (From Ref. 96.)...

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