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Frequently Asked Questions

We’ve compiled answers to the most common questions about our lasers, including their features, applications, and technical specifications. Whether you’re curious about tunability, ultra-narrow linewidths, or how our lasers can be integrated into your systems, this page is designed to help. If you don’t find the answer you’re looking for, feel free to reach out to our team – we’re always here to help!

COMET – Swept Source Laser

The laser controller appears as a “Virtual Com Port” when connected via USB to a computer. This serial interface is also accessible via the RX/TX pins of the DE-9 connector at the laser housing. Communication is based on low-level serial commands. For convenience, we can provide a Python library which includes a wrapper for these low-level commands, as well as advanced functions such as sweeping and setting the laser wavelength.

The COMET supports both operation modes, namely the “steady” tuning mode and the “swept” mode. Using the “steady” mode, the laser can be tuned within the tuning range with step sizes specified by the resolution.

The COMET can sweep without mode hops over approximately 0.25 nm, which is limited due to the laser design and the maximum phase shift of the heater actuators. For a wide-range sweep, the laser sweeps in quasi-continuous way. After every 0.25 nm sweep the laser hops from one cavity mode to the next. The mode hop takes less than 0.5 ms, during which time the laser restarts at the next mode. The result is a continuous wavelength sweep, with power dips during the mode hops. To ensure predictability for repetitive sweeps, all modes are indexed, and the mode hops happen at fixed wavelengths.

The laser provides a trigger signal at the start and end of each sweep, from the 1st SMA connector on the COMET adapter. This trigger signal can be fed into the trigger input of an oscilloscope for sweep synchronization.

In addition, the 2nd SMA connector on the COMET adapter provides a high signal during mode hops, which can be used to mask data points measured during mode hops.

We can only calibrate the COMET for one value of the sweep rate. The sweep performance will be optimal for that sweep rate. Nevertheless, the user can configure the sweep rate using the included software. The sweep performance can be suboptimal if the configured sweep rate differs significantly from the calibration value.

The relation between resolution and wavelength range is given by the maximum number of wavelength entries. The reason is that a maximum of about 13k wavelength entries can be stored in the device memory. For example, a wavelength range of 50 nm with 5 pm resolution requires 10k wavelength entries, which fits in the device memory.


The relation between scan rate and resolution is given by the time interval per wavelength step. This time interval should be maximally 0.5 ms and preferably 0.1 ms for a smooth sweep, due to matching with the heater bandwidth. For example, 5 pm wavelength resolution with a time interval of 0.1 ms gives a sweep rate of 50 nm/s.

Yes, we offer a modulation input (SMA connector) to modulate the laser diode current. Modulating the laser current enables fine analog control of the laser frequency, within a limited frequency range (typically up to ~1 GHz). We advise to use the modulation input only for the “steady” tuning mode, but not for the “swept” mode.

Our standard product does not include an isolator, but we can offer a built-in isolator as an add-on.

It is perfectly fine to use the laser immediately after switching on. However, optimal laser stability is reached when the laser is in thermal equilibrium with its surroundings (e.g. a heat sink), which is in 1-hour after warming up.

ATLAS – Wavelength Tunable Laser

Yes, the ATLAS is a complete tunable laser system. However, a computer is required to operate the laser, as the laser has no hardware user control.

The laser controller appears as a “Virtual Com Port” when connected via USB to a computer. This serial interface is also accessible via the RX/TX pins of the DE-9 connector at the laser housing. Communication is based on low-level serial commands. For convenience, we can provide a Python library which includes a wrapper for these low-level commands, as well as advanced functions such as setting the laser wavelength.

No, but our COMET laser offers both wavelength tuning and continuous sweeping.

Our standard product does not include an isolator, but we offer a built-in isolator as an add-on for the product versions with a central wavelength around 1550 nm.

The default wavelength resolution can be found in the specifications of the laser. We can calibrate the laser for smaller wavelength steps, but at the expense of the wavelength range. The reason is that a maximum of about 13k wavelength entries can be stored in the device memory. Ultimately, the D/A converters used for the heater drivers limit the minimum wavelength and frequency resolution to the order of 0.01 pm or 1 MHz, respectively.

Yes, we offer a modulation input (SMA connector) to modulate the laser diode current. Modulating the laser current enables fine analog control of the laser frequency, within a limited frequency range (typically up to ~1 GHz).

This is not supported by default. However, we are open to customizing the hardware and software to your preferences.

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 graph showcasing the laser short term stability in both output frequency and power.

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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