{"title":"THz Optics","description":"\u003cp\u003eReflective and refractive optics for the terahertz band. Gold-coated off-axis parabolic mirrors are achromatic and dispersion-free; TPX lenses provide a compact alternative with near-zero dispersion across the terahertz band.\u003c\/p\u003e","products":[{"product_id":"thz-off-axis-parabolic-mirror-oap2612-through-hole","title":"90 deg Off-Axis Parabolic Mirror, Through Hole Parallel to the Focused Beam, 2\", RFL 152.4 mm, Protected Gold","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eThis is the through-hole off-axis parabolic mirror in the configuration where the hole runs parallel to the focused beam, which means it is perpendicular to the parent optical axis. Optically it is identical to the plain 2-inch 90 degree protected-gold parabola: 50.8 mm diameter, 152.4 mm reflected focal length, lambda\/8 RMS figure and better than 95% average reflectance from 700 to 2000 nm.\u003c\/p\u003e\n\u003ch2\u003eWhen to choose this orientation\u003c\/h2\u003e\n\u003cp\u003ePick the focused-beam orientation when the auxiliary beam has to travel along the converging or diverging side of the mirror - for example when a probe beam is introduced from behind the mirror and brought to the same focus as the terahertz beam, or when a sample needs to be viewed on axis from behind the focus. Because the hole opens toward the focal point, alignment is done against the focal spot rather than against the collimated section.\u003c\/p\u003e\n\u003ch2\u003eWhy a reflective relay in the THz band\u003c\/h2\u003e\n\u003cp\u003eOff-axis parabolic mirrors are the standard way to collimate and focus terahertz radiation. Refractive optics are avoided because most materials introduce strong absorption and dispersion across the band, whereas a metal-coated reflector is achromatic from 0.1 to beyond 10 THz and adds no chirp to a single-cycle pulse. The protected gold coating stays above 95% average reflectance from 700 to 2000 nm and above 93% from 2 to 30 um, and its reflectance remains high throughout the terahertz band, so the same mirror also works for visible or near-infrared alignment.\u003c\/p\u003e\n\u003ch2\u003eAlignment and handling\u003c\/h2\u003e\n\u003cp\u003eA typical terahertz time-domain setup uses four off-axis parabolic mirrors: one to collimate the diverging beam from the emitter, one to focus onto the sample, one to recollimate after it, and a final one - usually a through-hole part - to focus onto the detection crystal. Set the beam height once and hold it across the whole table. The gold coating is soft and only lightly protected: never touch or wipe the optical face, and remove dust with dry nitrogen only.\u003c\/p\u003e\n","brand":"WaveQuanta","offers":[{"title":"Default Title","offer_id":48986393772186,"sku":"WQ-THZ-OAP2612-H","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/WQ-THZ-OAP2612-card-square_cd3db65e-251e-47fe-adda-72af73746f15.jpg?v=1786343980"},{"product_id":"thz-tpx-plano-convex-lens-tla25050","title":"TPX Plano-Convex THz Lens TLA25050, 25.4 mm Diameter, 50 mm Focal Length","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eTPX, or polymethylpentene, is one of the few polymers that combines low absorption with an almost flat refractive index across the entire terahertz band. That near-zero dispersion is what makes it usable for single-cycle terahertz pulses, where a dispersive material would stretch the pulse and destroy the time-domain waveform. The TLA25050 is a 25.4 mm diameter plano-convex lens with a 22.4 mm clear aperture and a 50 mm focal length.\u003c\/p\u003e\n\u003ch2\u003eRefractive versus reflective\u003c\/h2\u003e\n\u003cp\u003eOff-axis parabolic mirrors remain the first choice for a terahertz beamline because they are perfectly achromatic and introduce no material absorption. However, a lens is far more compact and far easier to align, since it needs only two degrees of freedom instead of the four or five of an off-axis parabola. For a compact instrument, for a sample-chamber window that also has to focus, or for a stage where the terahertz path is short and dispersion is not critical, a TPX lens is the pragmatic choice.\u003c\/p\u003e\n\u003ch2\u003eA useful alignment property\u003c\/h2\u003e\n\u003cp\u003eTPX is transparent in the visible, so a HeNe or diode alignment laser passes straight through the lens and can be used to set the optical axis, beam height and focus position before any terahertz radiation is generated. High-resistivity float-zone silicon, the other common terahertz lens material, is opaque in the visible and does not allow this. TPX is also light and easily machined, which keeps mount loading low.\u003c\/p\u003e\n\u003ch2\u003eDesign notes\u003c\/h2\u003e\n\u003cp\u003eOrient the convex face toward the collimated side to minimise spherical aberration. Because the refractive index of TPX is around 1.46 in the terahertz band, Fresnel reflection at each surface is a few percent and can produce a delayed etalon replica in the time-domain trace; if that replica falls inside the scan window, either increase the scan range so it can be windowed out, or slightly tilt the lens. Keep the lens inside the purged volume along with the rest of the terahertz path.\u003c\/p\u003e\n","brand":"WaveQuanta","offers":[{"title":"Default Title","offer_id":48986411368602,"sku":"WQ-THZ-LENS-TLA25050","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/WQ-THZ-LENS-TLA25050-card-square_df481ffd-fe95-4f6b-9207-5c2fac834526.jpg?v=1786343941"},{"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"},{"product_id":"thz-hdpe-lens","title":"HDPE THz Lens","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eHDPE is one of the two standard polymer lens materials for the terahertz band. It is inexpensive, low loss across a wide frequency range, easy to machine into large apertures, and mechanically forgiving. These lenses are made to 80\/50 scratch-dig with curvature held to 0.01 mm and diameter to 0.2 mm.\u003c\/p\u003e\n\u003ch2\u003eHDPE compared with TPX\u003c\/h2\u003e\n\u003cp\u003eThe two materials behave similarly in the terahertz band, and the choice usually comes down to two practical differences. TPX is transparent in the visible, so an alignment laser passes straight through it and the optical axis can be set before any terahertz is generated. HDPE is not, so alignment has to be done mechanically or with the terahertz beam itself. Against that, HDPE is cheaper and scales to large apertures more easily, which matters when the lens sits in a collimated section of a big beam.\u003c\/p\u003e\n\u003ch2\u003eRefractive versus reflective optics\u003c\/h2\u003e\n\u003cp\u003eGold off-axis parabolic mirrors remain the first choice for a terahertz beamline because they are perfectly achromatic and add no material absorption. A lens is far more compact and needs only two alignment degrees of freedom instead of four or five, so it wins wherever the layout is tight, the terahertz path is short, or the lens also has to serve as a chamber window.\u003c\/p\u003e\n\u003ch2\u003eDesign notes\u003c\/h2\u003e\n\u003cp\u003eOrient the convex face toward the collimated side to minimise spherical aberration. Fresnel reflection at each polymer surface is a few percent and can produce a delayed etalon replica in the time-domain trace; if that replica lands inside the scan window, either extend the scan so it can be windowed out or tilt the lens slightly. Keep the lens inside the purged volume along with the rest of the terahertz path.\u003c\/p\u003e\n","brand":"Swiss Terahertz","offers":[{"title":"Default Title","offer_id":48987927740570,"sku":"SWT-LENS-HDPE","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/SWT-LENS-HDPE-card-square_2c89b2ca-202a-4d39-9d64-483c03266487.jpg?v=1786343860"},{"product_id":"thz-tpx-lens-swiss","title":"TPX THz Lens","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eTPX, or polymethylpentene, combines low absorption with a refractive index that stays almost flat across the whole terahertz band. That near-zero dispersion is what makes it usable with single-cycle terahertz pulses, where a dispersive material would stretch the pulse and destroy the time-domain waveform. These lenses are finished to 80\/50 scratch-dig with curvature held to 0.01 mm.\u003c\/p\u003e\n\u003ch2\u003eThe alignment advantage\u003c\/h2\u003e\n\u003cp\u003eTPX is transparent in the visible. A HeNe or diode alignment laser passes straight through the lens, so the optical axis, beam height and focus position can all be set before any terahertz radiation exists. High-resistivity float-zone silicon, the other common terahertz lens material, is opaque in the visible and does not allow this. On a first build that difference alone can save a day.\u003c\/p\u003e\n\u003ch2\u003eWhen to use a lens instead of a mirror\u003c\/h2\u003e\n\u003cp\u003eOff-axis parabolic mirrors are achromatic and lossless in the terahertz band and remain the default for a research beamline. A TPX lens is the pragmatic choice for compact instruments, for a sample-chamber window that also has to focus, and for any stage where the terahertz path is short enough that dispersion and absorption are not the limiting factors. TPX is also light and easily machined, which keeps mount loading low.\u003c\/p\u003e\n\u003ch2\u003eDesign notes\u003c\/h2\u003e\n\u003cp\u003eOrient the convex face toward the collimated side. With an index near 1.46 the Fresnel reflection at each surface is a few percent, which can create a delayed etalon replica in the time-domain trace; extend the scan range so the replica can be windowed out, or tilt the lens slightly. Keep the lens inside the purged enclosure with the rest of the terahertz path so that water-vapour lines do not appear in the spectrum.\u003c\/p\u003e\n","brand":"Swiss Terahertz","offers":[{"title":"Default Title","offer_id":48987929018522,"sku":"SWT-LENS-TPX","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/SWT-LENS-TPX-card-square_012c3cbf-38a1-4993-9d0b-39a5fbbc1632.jpg?v=1786343848"},{"product_id":"thz-tpx-windows","title":"TPX THz Windows","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eTPX windows let a terahertz beam pass into or out of an enclosure with minimal loss and essentially no dispersion. They are the standard window for nitrogen purge boxes, sample chambers and detector housings on a terahertz beamline, finished to 80\/50 scratch-dig with diameter held to 0.2 mm.\u003c\/p\u003e\n\u003ch2\u003eWhy a window matters more than it looks\u003c\/h2\u003e\n\u003cp\u003eWater vapour absorbs strongly and structurally across the terahertz band, so any measurement made in ordinary room air carries deep absorption lines that have nothing to do with the sample. The standard remedy is to enclose the whole terahertz path and purge it with dry nitrogen, and that enclosure needs windows that do not themselves distort the pulse. A dispersive or lossy window would defeat the purpose.\u003c\/p\u003e\n\u003ch2\u003eTPX compared with silicon\u003c\/h2\u003e\n\u003cp\u003eTPX is visible-transparent, light, cheap and easily machined into large sizes, and its index is low enough that surface reflections are modest. High-resistivity silicon has a much higher index and therefore stronger surface reflections, but it is far more rigid and holds a pressure differential, which is why silicon is the usual choice for a vacuum window and TPX for an atmospheric purge enclosure.\u003c\/p\u003e\n\u003ch2\u003eDesign notes\u003c\/h2\u003e\n\u003cp\u003eFresnel reflection at each face produces a delayed replica of the pulse in the time domain. With a thin window that replica lands close to the main pulse and can be hard to separate, so specify thickness with the intended scan range in mind, or tilt the window slightly so the replica walks out of the beam path. Allow enough clear aperture for the beam at the window position, which in a collimated section can be much larger than at the focus.\u003c\/p\u003e\n","brand":"Swiss Terahertz","offers":[{"title":"Default Title","offer_id":48987930787994,"sku":"SWT-WIN-TPX","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/SWT-WIN-TPX-card-square_a08453de-36d2-456d-9a33-937cc0b360a2.jpg?v=1786343838"},{"product_id":"thz-silicon-windows","title":"High-Resistivity Silicon THz Windows","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eHigh-resistivity silicon has the flattest refractive index and among the lowest absorption of any terahertz window material, which makes it the reference choice where optical performance and mechanical strength both matter. These windows are finished to 80\/50 scratch-dig with diameter held to 0.2 mm and curvature to 0.01 mm.\u003c\/p\u003e\n\u003ch2\u003eWhere silicon is the right answer\u003c\/h2\u003e\n\u003cp\u003eSilicon is rigid enough to hold a pressure differential, so it is the standard window for vacuum chambers and cryostats, where a polymer window would flex or fail. It is also the usual material for terahertz beam combiners, because a thin silicon plate can transmit a near-infrared probe while reflecting the terahertz beam, or the reverse, depending on geometry.\u003c\/p\u003e\n\u003ch2\u003eThe trade-off to plan for\u003c\/h2\u003e\n\u003cp\u003eThe refractive index of about 3.42 is high, so roughly 30% of the incident power is reflected at each uncoated surface and the internal etalon is strong. In a time-domain measurement this shows up as a clear delayed replica of the main pulse. Either specify the thickness so the replica falls outside the scan window, use a wedged part so the internal reflections walk off axis, or ask about anti-reflection treatment.\u003c\/p\u003e\n\u003ch2\u003ePractical notes\u003c\/h2\u003e\n\u003cp\u003eSilicon is opaque in the visible, so a visible alignment laser cannot be used through it; set the axis first with a TPX part or align mechanically. Handle by the edge and keep the faces clean, since surface contamination shows up more strongly in a high-index material. For any window in the terahertz path, state the beam diameter at that plane along with the aperture you need, so the part is not undersized in a collimated section.\u003c\/p\u003e\n","brand":"Swiss Terahertz","offers":[{"title":"Default Title","offer_id":48987931607194,"sku":"SWT-WIN-SI","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/SWT-WIN-SI-card-square_4188a9b1-15ef-4475-a0e6-89f52ce19137.jpg?v=1786343812"},{"product_id":"thz-objective-lens","title":"THz Imaging Objective Lens, 0.1 - 30 THz","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eThis is an imaging objective for the terahertz band, covering 0.1 to 30 THz, supplied with a camera adapter, an optical component bracket, a post-assembly mount and an adapter ring. Depending on configuration it weighs between 30 and 200 grams, so it mounts on standard optomechanics without special support.\u003c\/p\u003e\n\u003ch2\u003eWhat an objective adds to a THz camera\u003c\/h2\u003e\n\u003cp\u003eA bare terahertz camera records whatever field distribution reaches its focal plane array, which is useful for beam profiling but not for imaging an object. An objective forms an image of the sample onto the array, setting the field of view, the working distance and the achievable spatial resolution. Terahertz wavelengths are hundreds of micrometres to millimetres, so the diffraction limit is coarse compared with visible optics and the objective aperture is what determines whether you reach it.\u003c\/p\u003e\n\u003ch2\u003eApplications\u003c\/h2\u003e\n\u003cp\u003eReal-time terahertz imaging is used for non-destructive testing, security screening, moisture and layer-thickness mapping, and quality control on production lines. Terahertz radiation passes through paper, plastics, textiles and ceramics while being strongly attenuated by water and blocked by metals, so a straightforward transmission geometry reveals concealed structure and moisture distribution without ionising radiation.\u003c\/p\u003e\n\u003ch2\u003eIntegration notes\u003c\/h2\u003e\n\u003cp\u003eSpecify the object distance and the field of view you need, not just a focal length: in the terahertz band the two are tightly coupled and the sensible configuration depends on the camera format. The supplied adapter ring and bracket are designed to mate with microbolometer terahertz cameras, so state the camera model when ordering so the correct adapter is supplied.\u003c\/p\u003e\n","brand":"Swiss Terahertz","offers":[{"title":"Default Title","offer_id":48987931967642,"sku":"SWT-OBJ","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/SWT-OBJ-card-square_d39578e9-950e-4cda-a5ea-9706bf2cde91.jpg?v=1786343802"},{"product_id":"thz-off-axis-parabolic-mirror-through-hole-collimated-2in","title":"90 deg Off-Axis Parabolic Mirror, Through Hole Parallel to the Collimated Beam, 2\", RFL 152.4 mm, Protected Gold","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eThis is the through-hole off-axis parabolic mirror in the configuration where the hole runs parallel to the collimated beam, that is along the parent optical axis. Optically it matches the plain 2-inch 90 degree protected-gold parabola: 50.8 mm diameter, 152.4 mm reflected focal length, lambda\/8 RMS figure and better than 95% average reflectance from 700 to 2000 nm.\u003c\/p\u003e\n\u003ch2\u003eWhen to choose this orientation\u003c\/h2\u003e\n\u003cp\u003eThis is the orientation normally used for collinear electro-optic sampling in a terahertz time-domain spectrometer. The optical probe beam is passed through the hole along the collimated section and recombined with the terahertz beam on axis, so probe and terahertz arrive at the sampling crystal perfectly overlapped without a separate beam combiner such as an ITO plate or a pellicle. That removes one dispersive element from the probe arm and simplifies the geometry considerably.\u003c\/p\u003e\n\u003ch2\u003eWhy a reflective relay in the THz band\u003c\/h2\u003e\n\u003cp\u003eOff-axis parabolic mirrors are the standard way to collimate and focus terahertz radiation. Refractive optics are avoided because most materials introduce strong absorption and dispersion across the band, whereas a metal-coated reflector is achromatic from 0.1 to beyond 10 THz and adds no chirp to a single-cycle pulse. The protected gold coating stays above 95% average reflectance from 700 to 2000 nm and above 93% from 2 to 30 um, and its reflectance remains high throughout the terahertz band, so the same mirror also works for visible or near-infrared alignment.\u003c\/p\u003e\n\u003ch2\u003eAlignment and handling\u003c\/h2\u003e\n\u003cp\u003eA typical terahertz time-domain setup uses four off-axis parabolic mirrors: one to collimate the diverging beam from the emitter, one to focus onto the sample, one to recollimate after it, and a final one - usually a through-hole part - to focus onto the detection crystal. Set the beam height once and hold it across the whole table. The gold coating is soft and only lightly protected: never touch or wipe the optical face, and remove dust with dry nitrogen only.\u003c\/p\u003e\n","brand":"WaveQuanta","offers":[{"title":"Default Title","offer_id":48991953289370,"sku":"WQ-THZ-OAP2612-V","price":0.0,"currency_code":"SGD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/files\/WQ-THZ-OAP2612-card-square_95bfaafa-2773-4a6d-9c80-04a9af485916.jpg?v=1786347338"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0734\/6156\/3546\/collections\/wq-terahertz-optics-card.jpg?v=1786345966","url":"https:\/\/waveqvanta.com\/collections\/wq-terahertz-optics.oembed","provider":"WaveQuanta","version":"1.0","type":"link"}