The following fluids are used by Cleveland Crystals for index-matching crystal/window interfaces in several of our non-linear and electro-optic crystal products in order to reduce Fresnel reflection losses, minimize etaloning problems and improve transmission wavefront quality. These fluids can be purchased in small quantities from Cleveland Crystals. We also have available a complete refill kit, as described later in this technical information sheet.
 

FC-43  A general purpose perfluorocarbon fluid manufactured by 3M Company. It is chemically very stable, non-toxic and compatible with all of our crystals and housing parts. Its primary drawback is a low refractive index, resulting in Fresnel losses of nominally 0.6% per surface when index-matching to glass, quartz or KDP type crystals.

FC-104 Similar to FC-43, but transparency extends further into the UV. Its higher volatility makes it more difficult to contain.
 

DECALIN Decahydronaphthalene¹, a highly characterized spectrographic solvent manufactured by Eastman Kodak Company. It is chemically quite stable under intense 1064 nm and 1315 nm irradiation and harmonics as well as most of the near IR-VIS-UV range. Breakdown can occur near certain frequencies representing C-H bond vibrational resonance and its harmonics. For this reason, it is not recommended for Alexandrite laser Q-switches. The primary advantage of decalin over the perfluorocarbons is its higher refractive index, typically resulting in Fresnel losses of roughly 0.01% and greatly reducing etaloning problems. Decalin should be kept away from open flame and handled with adequate ventilation and gloved hands. Care should be taken that housing parts and handling equipment are compatible with this solvent fluid.

1 - For details, ask for Publication #306, "cis-and trans-Decalin", American Petroleum Institute, Publication and Distribution Section, 2101 L Street, Northwest, Washington, DC 20037
 

CARGILLE 5040 A mixture of mineral oil and hydrogenated terphenyls manufactured by Cargille Laboratories, Inc. Although the least stable of the fluids we use, it has proven adequate for very low average energy/high instantaneous power applications at 1064nm, e.g., in large aperture (TX) Pockels cells used in laser induced fusion experiments. Its primary advantages are that the refractive index can be adjusted with high accuracy over a range of values near 1.5 and also that its low vapor pressure makes it easy to contain over long periods of time.

Room Temperature Properties of Index-Matching Fluids (IMF)

IMF	Refractive Index	UV Edge  = 0.6cm-1	Density  (g/cc)	Vapor Pressure  torr	Kinematic Viscosity  cs
FC-43	1.29	246nm	1.88	0.3	2.6
FC-104	1.27	210nm	1.75	29	0.8
Decalin	1.48	195nm	0.87	1.5	2.9
Cargille	1.50	375nm	0.89	<0.1	21

CONTENTS:

• 2cc glass syringe with male Luer fitting.
• 10cc vial index-matching fluid (specify FC-43 or decalin -- Cargille 5040 or FC-104 not supplied in IMX refill kit) .
• 18 gage x 2" stainless steel blunt syringe needle.
• 22 gage x 1/2" stainless steel blunt syringe needle.
• 24 gage teflon extension tubing.
• 5 disposable syringe filters

(1) Drop fluid into the fill hole, one drop at a time, so that the air has a chance to migrate out the fill hole between drops. To facilitate this migration, you can tap the Q-switch against your work surface, alternately on one end then the other, at the rate of a few taps per second, but keep the Q-switch nominally in the horizontal position.

(2) Alternatively, you can add the teflon extension tubing to the #22 needle and insert the tubing into the fill hole and along a narrow fluid channel (3/16" below the top of the fill hole) running perpendicular to the fill hole toward either end of the Q-switch. Push the tubing all the way into one channel or the other and push the syringe plunger until fluid and air bubbles purge out the other fluid channel. Continue depressing the plunger as you withdraw the tubing. It is advisable to hold an absorbent clean room wipe next to the fill hole to catch excess fluid, but be careful not to get contamination into the hole.

When finished dispensing fluid, replace fill screw.

NOTE: To avoid potential problems with differential thermal expansion between fluid and housing parts, it is desirable to leave at least 1/8"-1/4" long air bubble when fluid filling. This bubble will usually appear next to a polished face of the crystal if the housing is held vertically. Because of our small crystal/window spacing, capillary action prevents such a bubble from entering the aperture area.

If the fill kit is to be reused, remove the filter holder and shake vigorously to remove excessive fluid from contact with filter and holder. Store syringe parts, filter holder and needle separately in a clean place.

NOTE: If the fluid is decalin, it is important to prevent long-term contact between the fluid and the filter because of a slight long term chemical incompatibility, which may harm these parts or result in organic contamination of future dispensed fluid. We recommend using a new filter if decalin is to be dispensed more than 1 week after initial use. These are available from Cleveland Crystals.