{"product_id":"thz-filters-bandpass-bandstop-lowpass-highpass","title":"THz Filters: Bandpass, Bandstop, Low Pass and High Pass","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eA terahertz filter set is what turns a broadband source into a controlled measurement. These filters cover bandpass, bandstop, low pass and high pass forms with peak transmission typically above 90%, central frequency held to better than 5% as standard and to better than 1% on request, and apertures up to 150 mm for large-beam work.\u003c\/p\u003e\n\u003ch2\u003eWhy filtering matters in THz\u003c\/h2\u003e\n\u003cp\u003eBroadband terahertz sources emit across several octaves, and detectors respond across much of that range. Without filtering, a measurement at one frequency is contaminated by everything else the source produces, and water-vapour absorption lines elsewhere in the spectrum show up as unexplained structure. Selecting a band before the detector removes that ambiguity and usually improves signal to noise at the same time, because out-of-band power that only contributes noise is rejected.\u003c\/p\u003e\n\u003ch2\u003eChoosing a type\u003c\/h2\u003e\n\u003cp\u003eBandpass filters isolate a frequency of interest and are the usual starting point for imaging and for narrowband sensing. Bandstop filters remove a specific unwanted line, for example a strong source artefact. Low pass filters are the standard way to reject the high-frequency tail and any residual near-infrared leakage, and high pass filters do the reverse. Where rejection outside the band is critical rather than merely useful, the high-rejection bandpass type is the correct choice.\u003c\/p\u003e\n\u003ch2\u003eSpecification notes\u003c\/h2\u003e\n\u003cp\u003eCentral frequency and bandwidth are both customisable, so specify the physical quantity the experiment needs rather than picking from a catalogue grid. State the required aperture together with the beam diameter at the filter position: filters are often placed at a collimated section where the beam is much larger than at the focus, and an undersized filter will clip the beam and distort the measured spectrum.\u003c\/p\u003e\n","brand":"Swiss Terahertz","offers":[{"title":"Default Title","offer_id":48987927216282,"sku":"SWT-FILTER","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/SWT-FILTER-card-square_9fe0a5a9-c60f-43d7-9ac6-bb4b5f912aaf.jpg?v=1786343871","url":"https:\/\/waveqvanta.com\/products\/thz-filters-bandpass-bandstop-lowpass-highpass","provider":"WaveQuanta","version":"1.0","type":"link"}