Specifications

4 Chapter 1. Introduction
384.0 384.1 384.2 384.3 384.4
Frequency (THz)
External cavity
Diode cavity
Diode gain
COMBINED
Filter
Figure 1.3: Schematicrepresentationforthevariousfrequency-dependent
factors ofanECDL,adapted fromRef. [4],forwavelength λ = 780nmand
external cavity length L
ext
=15mm.
1.4 Temperature and current
Thelaser frequencyis alsodependenton temperature andinjection
current; thesensitivities aretypically 3MHz/µAand 30GHz/K[5].
Thus,low-noisestableelectronics,suchastheMOGLabsDLC ex-
ternalcavitydiodelasercontroller,areessential(seeRef.[6])to
achieve sub-MHz linewidth and stability.
AcriticalaspectofanECDL istemperaturecontrolofthecavity,since
the laser frequencydepends onthecavity length andhence onthe
thermalexpansioncoefficientofthecavitymaterial[4]. Thecavity
canbemachinedfrommaterialswithlow thermalexpansioncoeffi-
cient buteven thenthe passive stabilityis inadequatefor research
applications. Activefeedbackofthecavitytemperaturecombined
withcavitylengthcontrolprovideaflexibleandstableapproach.
TheMOGLabsCEL uses a negative temperaturecoefficient(NTC)
thermistortosensethecavitytemperatureandPeltierthermoelec-
tric cooler (TEC) to heat and cool the cavity material.