Frequently Asked Questions
Modulation
Yes, we offer corresponding laser drivers with a modulation input (SMA connector) to modulate the laser diode current. Modulating the laser current enables lasers frequency and amplitude modulation. This is useful, e.g., for spectroscopy and FMCW (frequency-modulated continuous-wave) technology.
When using the supplied laser driver for modulating the laser diode current, the 3-dB modulation bandwidth is 6 MHz. This bandwidth limit is imposed by the driver. In principle, the diode current can be modulated up to GHz frequencies with custom drivers.
The modulation amplitude is physically limited by the laser cavity FSR, which is typically about 4 GHz. To avoid mode hops during modulation, we recommended limiting the modulation signal for a slightly smaller modulation range.
Yes, using diode current modulation, the laser frequency can be chirped when applying the desired waveform. For laser current modulation, we offer a laser driver with a modulation input (SMA connector).
We do not offer pulsed lasers based on, e.g., mode-locking technology. We design our lasers for CW (continuous wave) emission. However, we can offer the laser with a modulation input to modulate the laser diode current.
Tuning
We can deliver the laser with a laser controller and corresponding software. On request, we can also provide a software-based wavelength calibration for the desired tuning range. Alternatively, all tuning knobs can be controlled manually via the software. An application note, included with the laser, explains this in more detail.
The continuous tuning range, without mode hops, depends on the tuning method, namely a) about 4 GHz (32 pm) when tuning the diode current or phase heater only. b) about 32 GHz (250 pm) for synchronous tuning of the phase section and ring heaters and c) about 5 GHz (40 pm) when only tuning the laser temperature. Note that the laser can also be tuned quasi-continuously by merging multiple continuous tuning ranges.
Due to technical and physical limits, the mode-hop-free tuning range is limited to approximately 250 pm. However, on request, we offer quasi-continuous tuning over a much larger range.
Currently, we only offer lasers based on thermo-optic tuning for the cavity phase and ring resonators by using resistive heaters placed on top of the respective waveguides.
Stability
This depends very much on the laser driver and operating condition. A typical long-term measurement for our laser can be found in this reference (see blue curve in Fig. 6). The frequency drift for this free-running laser remained within 350 MHz over 65 hours. Note that a correlation with the 24-h lab temperature cycle can be observed in this graph, which suggests that the free-running stability could be further improved with a stable ambient temperature.
A typical frequency noise measurement for the CF3/CT3 laser controlled with our laser driver is shown in the graph below. This measurement indicates a frequency noise density of about 2∙107 Hz2/Hz at 100 Hz and about 1∙106 Hz2/Hz at 1 kHz.
This depends very much on the laser setting, the driver and the operating condition. Please contact us about your specific requirements.
Feedback sensitivity
The laser performance can be significantly affected for a back-reflection level higher than –41 dB. To avoid any effect on the laser due to undesired back-reflections, we advise connecting an isolator to the laser output.
No, for a standard laser module no isolator is delivered. We can deliver an isolator on request. Otherwise, a standard off-the-shelve isolator is sufficient in most cases, for example from Thorlabs (IO-G-1550-APC or IOT-G-1550A) or any other supplier.
CF3
Yes, these lasers can be configured for other center wavelengths within the telecom C-band. We design these lasers to reach 1550 nm with low heaters powers on the ring resonators and cavity phase section. However, the laser can also be tuned to reach any other wavelength within the telecom C-band.
No, we do not manufacture this laser with a different laser diode. However, we offer calibration for other wavelengths in the telecom C-band.
CT3
We can calibrate the CT3 laser to scan in well-defined steps over a given range. Since our lasers are fully integrated (no moving parts), the repeatability is excellent. The scan range, resolution and speed are all mutually dependent. Please contact us with your specific requirements.
The CT3 laser model can typically provide up to 40 mW (16 dBm) for a maximum diode current of 300 mA. However, when calibrating the laser, we target a uniform, but somewhat lower output power (e.g. 14 dBm ± 0.3 dBm), over the full scan range.
We offer wavelength calibration for our CT3 laser model, which enables the user to enter the desired laser wavelength in the control software. An additional wavelength monitor is currently under development.
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