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Dichroic Beamsplitters

Dichroic Beamsplitters. M.Lampton UCB SSL Dec 2003. Why a dichroic beamsplitter?. Separating the VIS and NIR sensors could double our observing efficiency! with our present FIDO, a NIR photon arriving at a VIS detector is lost, ditto the reverse

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Dichroic Beamsplitters

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  1. Dichroic Beamsplitters M.Lampton UCB SSL Dec 2003

  2. Why a dichroic beamsplitter? • Separating the VIS and NIR sensors could double our observing efficiency! • with our present FIDO, a NIR photon arriving at a VIS detector is lost, ditto the reverse • but... would need two focal planes contrary to our FIDO decision • If we had twice the observing efficiency, perhaps we could.... • double the SN harvest? • or use a smaller telescope and payload? • or use fewer detectors? • etc M.Lampton Dec 2003

  3. Edmund Optics http://www.edmundoptics.com 1-800-363-1992 OCLI http://www.ocli.com 1-707-525-6957 Barr Associates http://www.barrassociates.com 1-978-692-7513 Omega Optical http://www.omegafilters.com 1-802-254-2690 Melles Griot http://www.mellesgriot.com 1-800-835-2626 Spectrogon US http://www.spectrogon.com 1-973-331-1191 Spectro-Film Inc www.spectrofilm.com 1-978-670-7192 Optical Coating Technologies www.coatingoptics.com 1-413-564-0700 North American Coating Labs www.nacl.com 1-866-216-6225 Opticorp Inc http://www.opticorp.com 1-978-250-8115 Dichroics are offered by many vendors… M.Lampton Dec 2003

  4. Technology“hot mirror” reflects IR, transmits VIS“cold mirror” reflects VIS, transmits NIR • Wideband substrate: borofloat, BK7, or silica • Multilayer dielectric layers on front side • Broadband antireflection coating back side • Typical application is removing heat from an illuminator (projector, microscope…) • Typical application subjects dichroic to sudden heat, many thermal cycles • Typical application does not demand high precision bandpass nor image quality M.Lampton Dec 2003

  5. Melles Griot M.Lampton Dec 2003

  6. Edmund cold mirrors M.Lampton Dec 2003

  7. Edmund extended hot mirrors“extended” means goes to 1.7um Transmission M.Lampton Dec 2003

  8. OCLI cold mirrors M.Lampton Dec 2003

  9. OptiCorp Inc M.Lampton Dec 2003

  10. Conclusions • Plenty of vendors! • Most of the commercial offerings are for simple “heat dump” applications, non imaging and not very critical of exact bandpass shape or stability • Tough! Withstand enormous thermal abuse. • Issues of sub arcsecond image quality and long term stability would need to be explored with one or more prospective vendors • Vendors are happy to bid on our requirements for stability, flatness, voids/flaws, stray, efficiency & curve shape, environmental, you-name-it. M.Lampton Dec 2003

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