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MOGlaser ECD-003 Options
Headboard and cable US$270 and $50
These are normally included with the MOGLabs DLC controllers. If
the laser is purchased separately, without controller, these are
almost certainly required.
Fold mirror US$270
When tuning the laser wavelength by rotating the grating, the output beam
direction will change. This can be corrected with a "fold
mirror"; see for example Rev. Sci. Inst.
72(2): 4477 (2001). During operation, the MOGlaser output beam direction does not change with frequency; it is only when manually adjusting the grating angle. Thus for most applications,
the fold mirror is not required and degrades the performance (increases susceptibility to vibration). If you will be working at one wavelength (e.g. Rb D2
line) then we recommend against this option.
Hermetic seal US$270
The laser cavity can be hermetically sealed with addition of cavity
exit windows and o-ring seal. The sensitivity to the effects of drafts and noise will
be reduced. Condensation due to operation at low temperatures will
also be minimised inside the cavity. Note that the seal is not vacuum tight.
The figure below shows the frequency change with time for an open cavity laser (see Hawthorn et al.) and the MOGLabs monoblock laser with hermetic seal. The wild excursions seen with the open cavity laser are due to someone walking around near the two laser systems; the MOGLabs laser is unaffected.
The figure below shows the frequency change with time for an open cavity laser (see Hawthorn et al.) and the MOGLabs monoblock laser with hermetic seal. The wild excursions seen with the open cavity laser are due to someone walking around near the two laser systems; the MOGLabs laser is unaffected.
Water cooling connections US$55
The laser base has a water cooling channel. Water cooling is
normally not required, but we offer quick-fit connectors to allow
easy water connection if required, for example to cool the laser
substantially below room temperature.
Faraday isolator US$1610
External cavity diode lasers are extremely susceptible to optical
feedback, and require some form of optical isolation for stable
single-frequency operation. We offer Faraday isolators
from EOT with 4mm diameter aperture, typically 37dB isolation and 85% transmission.
Anti-reflection coated diodes
We offer a range of diodes, from the standard 780nm/90mW diode which offers outstanding value, with good spatial mode quality and mode-hop free tuning range of up to 30GHz or more with current bias (discussed further below). We can also offer low-cost 150mW diodes at 780nm, 794nm, and 852nm with 0.25% reflectivity. They are a compromise with respect to spatial mode quality and mode-hop free tuning, but do offer net output power of 100 to 120mW.
For the ultimate performance (best spatial mode quality, smallest linewidth, and best tunability) we use diodes with ultra-low reflectivity coatings. These offer continuous frequency tuning without mode-hops,
or continuous variation of the output power, over a larger range. They are available at a range of wavelengths and power
ratings, in particular the 780nm 150mW option: the one diode can operate from 767nm to 820nm, with up to 150mW extra-cavity power (i.e. useful user-output).
Current bias
With the lower cost diodes, the injection current must be adjusted so that the internal diode
cavity frequency and external cavity mode frequency are matched. For a given frequency the choices of
current and temperature are limited and the output power cannot be
arbitrarily varied. If the diode injection current
(or the temperature) is adjusted, the laser is likely to
mode-hop, usually by about 40 GHz, the internal diode cavity spacing. The mode-hop free
tuning range is 10 GHz or more, with current bias
enabled. Current bias refers to varying the laser injection current
automatically as the frequency is adjusted or swept.
Diffraction gratings
We use gold-coated, sinusoidal holographic gratings, with diffraction
efficiency specified for reasonable compromise between frequency
stability and output power. Lower diffraction efficiency gratings can
be used to increase the output power by up to 20%, provided the
operating wavelength will be close to the diode gain peak wavelength,
and at the expense of reduced modehop-free scan range. Alternately,
even higher diffraction efficiency may be needed to pull the lasing
wavelength far from the gain peak of the diode. Depending on requirements, non-standard grating options are typically no extra charge, but can be up to US$300 in some cases.