The gain ridge length of the 795DBR laser is 1.5mm. The total DBR laser chip is 2mm in length, with 500um being the passive DBR grating. The effective cavity length is around 1.6 to 1.65mm.
For amplitude modulation, the diodes show a RIN peak at around 3.5GHz; however the TO8 packages are not optimized for RF design. The wire bonds and feed-troughs will add parasitics that can limit modulation, as well as any constrains from the drivers. Theoretically, the TO8 package is comparable to the butterfly package, where our customers have done sub-nsec pulses routinely as in the reference.
http://www.photodigm.com/picosecond-pulsed-laser-diode-nanosecond For frequency tuning, tuning coefficient with current at low frequencies is generally around ~ 2nm / A for all wavelengths. The thermal cutoff is around 100 KHz.
Typical:
The current tuning coefficient of a typical DBR laser is around 0.002nm/mA at low frequencies with the thermal cutoff around 10kHz-100KHz. So if the application requires frequency modulation, then +/-4.8GHz is doable. Although 350KHz rate is a little on the high side.
For amplitude modulation, the diodes show a RIN peak at around 3.5GHz, however the TO8 packages are not optimized for RF design. The wire bonds and feed-throughs will add parasitics that can limit modulation, as well as any constrains from the drivers.
Please check this application note; it has a fairly detailed description on the performance comparisons of ECDL versus DBR/DFB lasers. http://www.vescent.com/technology/short-cavity-lasers/ . We believe that in most hyperfine spectroscopic applications, Photodigm's DBR lasers can be applied in place of an ECDL thanks to the DBR's excellent stability and narrow line width. The following is another table comparing ECDL and DBR.
780nm |
ECDL |
DBR |
Power |
50mW |
300mW |
Linewidth |
<200kHz |
<500kHz |
Tuning range |
765-781 nm |
779.5-781.5 |
Mode hop free tuning |
15nm |
2nm |
Size |
2,650 cm3 |
<1cm3 |
Scalable |
No |
Yes, monolithic |
Price |
Mid-range |
Volume discount |
Beam diversion: typical 6° FWMH slow axis (horizontal) and 28° FWMH fast axis (vertical) Waist size: Our wave-guide software generated beam size is defined different from conventional, so we normally estimate the near field beam waist through the far field divergence measurement. With the FWHM divergence at 6 and 28 degrees for slow and fast axis, the estimation will be 6.7um and 1.4um 1/e2 beam waist for the 795nm DBR and 7.2um and 1.5um 1/e2 beam waist for the 852nm DBR.
Emission position: An aperture sits in the middle point of the TOSA window, i.e., 2.6mm from the base of package and 2.9mm from the side of package. In the direction of light emission, the aperture is 1.05 mm max from the outer edge of package.
Connection: The TOSA flex cable is compatible with ZIF connectors such as Digi-Key Part #WM6762CT-ND. Our TOSA heat sink mount provides conventional Dsub D9 and D15 connector to laser driver and temperature controller.
Our TOSA package is ideal for various applications. For simple lensing, we see a decent beam using a fast aspheric (NA of .55 or better) such as these, please follow link provided.
http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3811
The slow axis beam divergence is 6° FWHM typical, 8° maximum. The fast axis beam divergence is 28deg FWHM typical, 32° maximum. The laser facet to the outer edge of the TOSA package is 1.35mm maximum. In addition, the DBR laser is polarized with ER around 20dB. The polarization of the E field is horizontal by design (looking into the laser ridge from front facet, p side up, n side down).