400nm 대역 통과 필터

Context: A common-path non-collinear optical parametric amplifier (NOPA) system used for generating ultrashort laser pulses.

Usage of Filter: A 400nm bandpass filter (specifically with a ~40nm bandwidth) is placed in the optical path of the pump beam, after the second harmonic generation stage and before the amplification crystal.

Function: It acts as a spectral cleaner, transmitting the generated 400nm pump light (second harmonic of the 800nm source) while blocking the residual 800nm fundamental light and other unwanted spectral components.

Result: Provides a clean, high-contrast pump beam for the parametric amplification process, enhancing the efficiency and stability of the amplified signal.

Context: An optical system for quantifying the electric charge density at the interface of a material (e.g., a membrane or particle) using Second Harmonic Generation (SHG) spectroscopy.

Usage of Filter: A 400nm bandpass filter is positioned in the detection path, in front of the photomultiplier tube (PMT) or detector.

Function: It selectively isolates the Second Harmonic Generation signal (which is at 400nm when the sample is excited by an 800nm laser) while rigorously blocking the intense reflected fundamental 800nm light.

Result: Allows for the precise detection of the weak SHG signal generated at the interface, which is directly correlated to the interfacial potential and charge density.

Context: A portable fluid analysis apparatus designed to measure optical properties (like fluorescence or absorbance) of a fluid sample, often for medical or environmental testing.

Usage of Filter: A bandpass filter centered at or including the 400nm region (e.g., 400-425nm range) is located in the detection channel after light has passed through or interacted with the fluid sample.

Function: It filters the light emerging from the sample to ensure that only the specific wavelength band of interest (e.g., a fluorescence emission or specific absorption band around 400nm) reaches the sensor.

Result: Maximizes the signal-to-noise ratio for the target analyte, ensuring accurate quantification of the fluid's properties even in the presence of ambient light or other spectral noise.