Notch filter, holographic

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. 

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... 

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.)...

The Raman spectra on solid metal substrates were measured using a Renishaw RM2000 micro-Raman apparatus, coupled with a diode laser source emitting at 785 nm. Sample irradiation was accomplished using the 50x microscope objective of a Leica microscope DMLM. The beam power was 3 mW, the laser spot diameter was adjusted between 1 and 3 pm. Raman scattering was filtered by a double holographic notch filter system and collected by an air-cooled CCD detector. The acquisition time for each measurement was 10 s. All spectra were calibrated with respect to a silicon wafer at 520 cm. ... 

Figure 8.16. Transmission curves for holographic notch hiter (HNF) and holographic super notch filter (HSNF) for a 514.5 nm Ia.ser. (Adapted from Reference II, with permission.)...

Figure 11.6. Schematic of holographic notch filter used to inject laser beam into the collection axis of a microscope (similar to an arrangement in a Renishew Raman microscope system).

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