Lasers and optics:
  • Thorlabs - Thorlabs is my personal favorite. Good quality, good prices, ingenuous products and the place to buy from when you are in a hurry. Thorlabs has excellent customer service.
  • Newport - Newport is a reputed company to buy from when it comes to optics and opto-mechanics. They have a reputation for high quality and high prices. Good customer service, a bit slow to respond to emails. Somewhat slow to deliver equipment.
  • CVI + Melles Griot -  Coherent - Edmund Optics - Karl Lambrecht Corporation - Lambda Research Optics - Qioptiq - Altechna
    These companies supply all kinds of optical components (polarizers, waveplates, lenses, beam splitters, prisms, filters, etc.), as well as optical holders, opto-mechanics, posts, post holders and many more useful things.
  • Eagleyard Photonics - Toptica - Frankfurt lasers
    Photonics and laser stuff, especially laser diodes.
  • OWIS - Optics, opto-mechanics, manual and motorized positioning. I visited a very good lab that uses exclusively OWIS components and heard only positive things about the company.
  • EKSPLA - Vm-Tim  - EKSMA Optics - Optics, opto-mechanics, nonlinear and laser crystals, lasers and others.
  • Horiba Jobin Yvon - Spectroscopy equipment.
  • Ocean Optics - Spectroscopy, their USB4000 series are compact, handy devices which are very useful in the lab.
  • Stellar Net - Spectroscopy, especially USB spectrometers.
  • Avantes - Spectroscopy, including USB spectrometers.
  • B&W Tek - Spectroscopy, including USB spectrometers.
  • Schott - Glasswork, filters and lenses.
  • Hellma - Glasswork, all kinds of beautiful cells, including flow cells.
  • Cascade Laser Corp. - Provides laser components and laser accessories. Especially, they have very good Infrared Viewers, great for Ti:Sapphire lasers but unfortunately going only to 1550 nm, so not for all OPAs.
  • Cristal Laser - Raicol Cristals - Casix:Provide crystals for lasers. Of interest for nonlinear optics are the BBO, KTP, etc.
  • Spiricon - Is a supplier of beam diagnostic tools
  • AHF analysentechnik - offers inovative filters for optical systems.

Electronics:

  • Stanford Research Systems is an excellent provider of measurement equipment (lock-in amplifiers, preamplifiers, boxcar integrators, photon counters). They also have a very good optical chopper - the SR540.
  • Signal Recovery - Lock-in amplifiers, boxcar averagers, preamplifiers, optical choppers, etc. I have no direct experience with this brand but have seen them in other labs and, well, they are on the market.
  • Tektronix is simply the best provider of oscilloscopes.
  • Kepco manufactures high quality DC and AC powers supplies.
  • Brandenburg - A British power supply company that offers stable power supply units for the lab in general and for photomultipliers in particular.
  • Scitec Instruments- They have laser, optics, crystals infrared detectors, lock-in amplifiers but most of all they offer a wide range of optical chopper blades.
  • Keithley Instruments - All sorts of electronics of use for the lab.

Photo detectors:

  • Hamamatsu photonics sells all kinds of photodiodes, photomultiplier tubes, modules and the required power supplies.
  • Perkin Elmer Optoelectronics - Several optical detectors, from photodiodes to CCD cameras. A point of interest are the Channel Photomultipliers (CPT) and the single photon counting modules.
  • ET Enterprises Ltd., Electron Tubes - Provides a large variety of photomultiplier tubes.
  • id Quantique - Appropriately named, this Swiss company focuses on quantum and classical cryptography. They provide single photon sources and single photon counters too. The id 100 photon counter is definitely worth checking out for its timing resolution (40 ps at FWHM) and I like the low dark counts too (< 2 Hz). Active area diameter is 20 or 50 microns. Perhaps best suited for microscopy.
  • Photonis - another supplier of photomultiplier tubes.
  • Sens-Tech is another sensor company offering a wide range of detectors.

Magnetics:

  • GMW is a distributor of permanent magnets and electromagnets. They also have some measuring equipment. The 3470 electromagnet for applications on an optical table is a personal favorite of mine.

Microscopy:

  • Olympus - I have seen several of the IX2 series microscopes in operation and people seem to be happy with them. Great customer service and also seems great for buying accessories.
  • Zeiss - I have some experience with the LSM 510 META - a fantastic instrument.
  • Leica - Only heard about them being well represented in Europe.
  • Nikon - Apparently coming on the European market.

Others:

  • Oxford Instruments has a entire range of cryostats for optical applications. Ideal for studies of optical properties at low temperatures.
  • NMLaser Producs offers a range of mechanical shutters for optical applications. I have heard good things about their products.