Spectroscopic slabs (or prisms) are core components in optical systems, their working principle can be summarized into the following key points:‌12

I. Basic Optical Phenomena

1. ‌Reflection and Transmission‌
2. When incident light encounters the surface of a spectroscopic film, part of the light is reflected and the other part transmitted. The ratio of this split is determined by the surface coating characteristics, for instance, a neutral spectroscopic film can achieve 50% reflection and 50% transmission without selectivity to wavelengths.
3. ‌Interference and Multilayer Film Design‌
4. Birefringent Spectral Filters - Achieve wavelength selectivity through the stacking of multiple dielectric films, utilizing the interference effect of light. For example, short-pass filters reflect short-wavelength light and transmit long-wavelength light, while long-pass filters do the opposite.

II. Core Categories and Characteristics

• ‌Structure Type‌‌Flat Plate Spectral FilterSimple structure, low cost, suitable for space-limited environments
• ‌Cubic SpectrometerHigh stability, commonly used in precision optical systems
• ‌Function Type‌‌Polarized Beam Splitter (PBS)Separate P-polarized light (transmitted) from S-polarized light (reflected)
• ‌Non-polarized beam splitter (NPBS)Maintain the polarization state of the incident light, splitting only according to a fixed ratio.
• ‌Bichromatic diffraction gratingSeparate light by wavelength (e.g., reflect red, transmit green, blue; transmit red, green, reflect blue, etc.)

III. Key Parameters

• ‌Reflectance/TransmittanceLight energy distribution ratio at a specific wavelength
• ‌Angle toleranceStability of performance with variations in the incident angle
• ‌Bandwidth CharacteristicsNarrowband (high resolution) and Broadband (suitable for wide spectrum)

Section 4: Typical Applications

1. Diffractive gratings are widely used in laser technology (beam control), excitation light separation, wavelength decomposition, and optical communication (signal routing) fields. Their low absorption characteristics make them indispensable in high-efficiency optical systems.