Custom Low-OH Quartz Capillaries

Parameter	Typical Range
OD	0.3–6 mm
ID (bore)	0.1–4 mm
Length	10–500 mm
Bore tolerance	±0.005–0.02 mm
Concentricity	≤5% of wall
Straightness	≤0.5 mm/m
Material grade	Confirmed per application, sent with your quote
OH content	Confirmed per application
Transmission at key wavelength	Confirmed per application

Inquiry

Low-OH quartz capillaries combine a controlled bore with a hydroxyl-content requirement for wavelength-sensitive optical assemblies. Select this material when absorption in the quartz affects the optical function, rather than treating low OH as a universal upgrade for every capillary.

Select Low-OH by Operating Wavelength

Start with the operating band and the distance light travels through, or interacts with, the quartz. A capillary used only to carry fluid, wire or a fiber may not benefit from a lower OH level. For an optical path, specify the transmission needed at the working wavelength together with the material grade, wall section and end-face finish.

OH Absorption Around 2.7 µm

Hydroxyl groups produce a strong absorption band near 2.73 µm. A suitable low-OH grade can reduce this absorption where it limits an IR optical path, but low OH does not guarantee transmission across the entire mid-IR spectrum. For UV service, use the actual grade’s spectral data: UV suitability also depends on impurities and material processing, and cannot be ranked by OH content alone.

Material Certificate and Transmission Verification

Put the named grade, maximum OH content and lot traceability on the purchase specification. Where transmission is critical, also define wavelength, optical path length, surface condition and the acceptance test. The grade comparison below is selection guidance; typical data for a reference specimen do not replace acceptance criteria for the delivered capillary. ID, OD and centering remain separate geometric requirements.

Material First

Specify OH Level and Target Wavelength Together

Controlled Feature	What to Put on the Drawing / PO
Quartz Grade	Named low-OH fused-quartz grade rather than a generic low-OH label
OH Content	Reference <5–10 ppmConfirm the actual grade certificate and acceptance limit before order
Target Wavelength	Operating band and any transmission requirement near the 2.7 µm OH absorption region
Bore ID	Finished ID and reference ±0.01 mm tolerance where geometry permits
Outer Diameter	OD and its fit requirement inside the holder or feedthrough
Concentricity	Bore position relative to the OD when optical alignment depends on it
Length / Ends	Finished length plus as-cut, ground or polished end requirement

Selection Logic

When Low-OH Is Functionally Necessary

System Condition	Why Material Grade Matters	Also Specify
IR laser or sensor path	Hydroxyl absorption can reduce transmission in wavelength-sensitive systems	Wavelength, path length and end-face finish
Semiconductor thermal equipment	Low-OH grade may be selected for clean, high-temperature optical or sensing paths	Process temperature and contamination requirement
Fiber or detector alignment	Material and bore geometry must be controlled in the same part	ID, OD, concentricity and axial length

Delivery Forms

Low-OH Capillaries Defined by Material and Geometry

Low-OH Round BoreIR-grade material with OD, ID and length controlled together

Alignment CapillaryCentered bore for fibers, wires and optical elements

Optical End FacesGround or polished faces where the capillary ends at an optical interface

Cut-to-Length InterfaceChamfered or finished ends for repeat assembly

Applications

Wavelength-Sensitive Capillary Uses

IR Laser AssembliesSmall-bore quartz guides selected around wavelength and OH requirement

Semiconductor SensorsLow-OH capillaries for high-purity thermal and optical instrumentation

Fiber & Detector PackagingPrecision bores that position an optical element inside an IR-grade quartz body

Need low-OH material with a precision bore?Send the target wavelength, OH limit, ID, OD, concentricity, length and end-face requirement.

Open the Capillary Configurator

Engineering Data

Grade-Qualified Material Purity

Electric-fused / flame-fused quartz: SiO₂ ≥99.99%; synthetic JGS1-grade fused silica: ≥99.999%. Grade and lot certificate govern supplied material.

Engineering Data

OH Content by Material Route

Route	Grade	Wavelength	OH	Use
Synthetic hydrolysis-fused silica	JGS1	185–2500 nm	≈1000 ppm	Deep-UV optics and lithography
Flame-fused natural quartz	JGS2	220–2500 nm	120–260 ppm	UV-visible windows and instruments
Vacuum-fused quartz	Grade-specific	UV–near IR; confirm grade	<3 ppm	Semiconductor and lamp components
Vacuum-fused low-OH quartz	JGS3	260–3500 nm grade classification	≤10 ppm	IR observation and low-OH components
Electric-fused continuously drawn quartz	Grade-specific	UV cut-off depends on grade	5–150 ppm; heat-treatment dependent	Lamps, heaters and optical-fiber support parts

The 2730 nm OH absorption peak is a selection criterion for infrared optical paths. A low-OH requirement must name the grade, ppm limit and lot-certificate acceptance.