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Unlike bandpass filters that isolate desired wavelengths, notch filters target and suppress specific frequencies—such as laser scatter, ambient noise, or harmonic distortions—without affecting the broader spectrum. This unique capability makes them indispensable in applications like Raman spectroscopy (blocking Rayleigh scatter), 5G telecommunications (filtering interference), and laser systems (suppressing harmonics). Our notch filters are manufactured using advanced thin-film interference technology (ion-beam sputtering, IBS) to achieve deep stopband attenuation (≥60dB), steep transition edges (<20MHz slopes), and low passband insertion loss (<1.5dB). With customizable stopband frequencies (175nm–10GHz) and form factors (12.5–100mm diameter), they meet the demands of diverse industries, from academic research to aerospace defense. Our filters also undergo rigorous environmental testing (temperature cycling, humidity, vibration) to ensure long-term stability (<0.5dB stopband attenuation drift per year).
High Rejection: Provides ≥60dB attenuation in the target wavelength range—equivalent to blocking 99.9999% of unwanted light—effectively eliminating interference. For example, a 532nm laser notch filter blocks 532±5nm light with 60dB attenuation, ensuring Rayleigh scatter (10⁶x more intense than Raman signals) does not overwhelm the detector. Stopband attenuation can be customized up to 80dB for ultra-low-interference applications (e.g., quantum communication) .
Customizable Stopbands: Available for standard laser lines (e.g., 266nm, 488nm, 532nm, 1064nm) and 5G NR bands (e.g., 2.4GHz, 3.5GHz, 5GHz) with precise cut-off frequencies. Stopband width options range from 1nm (for narrow laser lines) to 100MHz (for broadband interference, e.g., 5G adjacent-channel noise). We use electromagnetic simulation software (e.g., FDTD Solutions) to design custom stopbands that match specific interference profiles .
Broad Transmission: Low insertion loss (<1.5dB) outside the stopband, maintaining signal strength in desired wavelengths. For example, a 1064nm notch filter has <0.5dB insertion loss in the 800–1000nm and 1100–1700nm ranges, ensuring no significant power loss in NIR imaging or spectroscopy. Passband flatness is <1dB across the operating range, preserving spectral integrity .
Steep Transition Edges: Typically 20MHz slopes (for RF/microwave notch filters) or <5nm slopes (for optical notch filters) between passband and stopband to minimize signal distortion. A steep transition ensures the filter blocks only the unwanted wavelength range, avoiding attenuation of adjacent desired signals. For example, a 5GHz 5G notch filter with 20MHz slopes blocks 5.00–5.02GHz interference while transmitting 4.98–5.00GHz and 5.02–5.04GHz signals without distortion .
Dimensional Flexibility: Standard sizes complement our bandpass filters, with 12.5–100mm diameter options for optical notch filters and 5–50mm square/rectangular options for RF/microwave filters. Small diameters (12.5–25mm) fit compact systems (e.g., handheld Raman spectrometers), while large diameters (50–100mm) are designed for high-power laser systems (e.g., 1kW fiber lasers). Thickness options (1–3mm) balance mechanical stability and weight .
Surface Quality: Manufactured to 20-10 or 10-5 standards (per MIL-PRF-13830B) for reduced scatter in high-sensitivity systems. A 10-5 surface reduces light scatter in optical notch filters, ensuring no additional background noise in low-signal applications (e.g., single-molecule fluorescence detection). RF/microwave filters feature gold-plated surfaces for low contact resistance and high conductivity .
Raman Spectroscopy: Blocks intense Rayleigh scattering at the excitation wavelength while transmitting Raman shifts. For example, a 785nm notch filter blocks 785±2nm Rayleigh scatter (which is 10⁶x more intense than Raman signals) while transmitting 785±100nm Raman shifts, enabling detection of molecular vibrations (e.g., C-H bonds in hydrocarbons) with high signal-to-noise ratio .
Fluorescence Imaging: Eliminates laser excitation artifacts to enhance emission signal detection. In confocal microscopy, a 488nm notch filter blocks 488nm excitation light (used to excite fluorophores like GFP) while transmitting 500–550nm emission light, reducing background noise by >100x and improving image clarity of subcellular structures .
5G Infrastructure: Filters interference in 2400–2500MHz bands (used for Wi-Fi/Bluetooth) to improve 5G signal clarity. 5G base stations use notch filters to block 2.4GHz interference, reducing bit error rates (BER) by >50% and ensuring reliable communication. Custom notch filters are also designed for 3.5GHz and 5GHz 5G bands to mitigate adjacent-channel interference .
Satellite Systems: Reduces unwanted harmonics in communication links. Satellite transponders use notch filters to block harmonic frequencies (e.g., 2x or 3x the carrier frequency) generated by power amplifiers, preventing interference with other satellite channels and ensuring compliance with ITU (International Telecommunication Union) frequency regulations .
Laser Welding: Blocks stray laser wavelengths to protect sensors and operators. A 1064nm fiber laser welding system uses a notch filter to block 532nm second harmonic light (generated during welding) that could damage the vision system’s camera sensor, ensuring consistent weld quality and operator safety .
EMC Testing: Isolates specific frequency bands in electromagnetic compatibility (EMC) measurements. EMC test chambers use notch filters to block the frequency of the device under test (DUT), allowing detection of weak electromagnetic emissions (e.g., from medical devices) that would otherwise be masked by the DUT’s own signal .
Q: How is a notch filter different from a bandpass filter?
A: Notch filters block a specific wavelength range (stopband) while transmitting all other wavelengths (passband), whereas bandpass filters transmit a specific range (passband) and block all others. They often work together in spectroscopy setups—for example, a notch filter blocks Rayleigh scatter (stopband) while a bandpass filter isolates the desired Raman shift (passband). Notch filters are ideal for eliminating narrowband interference (e.g., single laser line, specific RF frequency), while bandpass filters are used to select broad or narrow desired wavelength ranges .
Q: What is the typical stopband width?
A: Our notch filters offer customizable bandwidths, with examples like 10MHz stopbands centered at frequencies between 1400–1700MHz (for RF applications) and 1–10nm stopbands for optical laser lines (e.g., 532±5nm). Stopband width is determined by application needs: narrow widths (1nm) for isolating single laser lines, wide widths (100MHz) for blocking broadband interference (e.g., 5G adjacent channels). We can design stopbands with widths as small as 0.5nm (for high-resolution spectroscopy) or as large as 1GHz (for wideband RF interference) .
Q: Can notch filters be used with high-power lasers?
A: Yes, our hard-coated variants handle moderate laser power (up to 1W/cm² CW at 532nm) for applications like laser imaging. For high-energy applications (e.g., pulsed lasers with >1J/cm² energy density, CW lasers with >10W/cm² power density), inquire about our high-damage-threshold variants. These use thicker substrates (3–5mm UV fused silica) and enhanced coatings (e.g., HfO₂/SiO₂) to achieve laser-induced damage thresholds (LIDT) up to 5J/cm² @ 1064nm, 10ns pulses. We also offer water-cooled mounts for extreme high-power applications (e.g., 100kW laser cutting) to prevent thermal damage .
Q: Are custom notch frequencies available?
A: Absolutely. We support custom stopbands across the 175–3200nm+ optical range and 1MHz–10GHz RF/microwave range, including laser lines (e.g., 355nm, 980nm), communication bands (e.g., 6GHz 5G, 28GHz satellite), and industrial frequencies (e.g., 13.56MHz RFID). Customization includes adjusting stopband center frequency, width, attenuation level, and passband insertion loss. We provide a design proposal with simulation results (e.g., transmission vs. wavelength) for customer approval before manufacturing, ensuring the filter meets specific system requirements .
