Stabilized laser device

Abstract

Systems, methods, and devices relating to a device for providing a stabilized laser output from a laser diode. A device produces a laser output from a laser module that uses a laser diode. A stabilized laser output is produced by providing a feedback loop that includes a reference block with a vapour cell that receives the laser output. The output of the interaction between the laser output and the element in the vapour cell is converted into digital data by way of an ADC and the digital data is processed by a DSP module. The processed digital data is converted into analog signals by way of a DAC and the analog signals are used to adjust and / or stabilize the parameters of the laser output. The DSP module may also receive user input to program / adjust laser output parameters.

Description

Attorney Docket No. 1805P001W001STABILIZED LASER DEVICETECHNICAL FIELD

[0001] The present invention relates to laser technologies. More specifically, the present invention relates to a unitary device that provides a stabilized laser output that, in some implementations, is user programmable.BACKGROUND

[0002] Many technologies rely on a complex system of stabilized lasers, with both frequency and power agility, to prepare, interrogate, and read-out information from systems such as quantum systems. For quantum related applications, these lasers may be essential for every single stage of building and operating quantum technologies.

[0003] Laser radiation is used to trap individual atoms and cool these atoms down to near absolute-zero. Laser pulses can then reconfigure the individual electrons inside the cold-trapped atoms in order to make quantum measurements and readout the quantum information such that the information can be used.

[0004] Some quantum computers need a complex system of between 5-10 stabilized lasers, each of which must have extremely precise control and agility over the laser properties such as frequency, power, and phase. Certain types of quantum sensors, such as gravimeters / accelerometers, or greenhouse gas sensors can be simpler, with some using just a single laser of fixed frequency and power to monitor changes such as phase, power, or polarization from the quantum object.

[0005] Stabilized lasers form the backbone of many of these quantum applications. Such stabilized lasers, however, suffer from a number of drawbacks. Once these lasers have been stabilized, multiple of these lasers can be combined, each with numerous narrow bandwidth modulators. Frequency and amplitude control is typically implemented using fixed circuits which must be custom designed and tested for each specific application. These larger scale systems can then createAttorney Docket No. 1805P001W001the required pulses of laser light needed to control the quantum system. To achieve the required performance, complete laser systems used for research and development are hand assembled from hundreds of individual lenses and mirrors in temperature controlled, vibration minimized laboratories, on room-sized optics tables that weigh up to 1000 kg.

[0006] Such traditional systems have two key failings. The first is that they are incredibly slow to build or modify. For one-off, or early-stage R&D projects with only one or two required laser systems, such an approach is acceptable. However, as more applications reach maturity, each with added complexity, the cost and schedule implications of having to complete an entire development process for each new laser configuration has become overwhelming. Laser systems can take years to build, and simple modifications to try new ideas can take months. The development cycle is thus incredibly slow.

[0007] The second key failing is that such laser systems are incredibly fragile and sensitive devices. Quantum labs are typically located in basements to reduce vibrations, temperature stabilized to at least 0.1 C (0.2 F), and commonly feature RF and magnetic shielding. As well, there are very large maintenance requirements — a 50% “up-time” would be considered extraordinary. This is primarily due to the extreme requirements of the lasers and electronics. For example, alignments of 0.5micro-meters across a 3m beam path are common - this means an alignment of 200 billionths of an inch across 10ft.

[0008] Given the above, there is therefore a need for systems and methods that provide a much simpler and much less expensive alternative that provides a laser output that is suitable for quantum applications as well as other for other application such as atomic and molecular spectroscopic technologies.SUMMARY

[0009] The present invention provides systems, methods, and devices relating to a device for providing a stabilized laser output from a laser diode. A device produces a laser output from a laser module that uses a laser diode. A stabilized laser outputAttorney Docket No. 1805P001W001is produced by providing a feedback loop that includes a reference block that receives the laser output. The output of the interaction between the laser output and an element in the reference block is converted into digital data by way of an ADC and the digital data is processed by a DSP module. The processed digital data is converted into analog signals by way of a DAC and the analog signals are used to adjust and / or stabilize the parameters of the laser output. The DSP module may also receive user input to program / adjust laser output parameters.

[0010] In a first aspect, the present invention provides a device for producing a laser output, the device comprising:- a laser module producing said laser output;- at least one control module that controls said laser output by adjusting parameters for said laser module by way of at least one or more of: current control and temperature control;- an A / D converter module that receives an analog output of a reference block after said laser output has interacted with said reference block and that converts said analog output into digital laser data;- a DSP block that receives said digital laser data and processes said digital laser data to produce processed digital laser data;- a D / A converter module that receives processed digital laser data from said DSP block and converts said processed digital laser data into analog signals for said at least one control module;wherein said parameters used by said at least one control module to control said laser output are based on said analog signals.

[0011] In a second aspect, the present invention provides a device for producing a laser output, the device comprising:- a laser module producing said laser output;Attorney Docket No. 1805P001W001- at least one control module that controls said laser output by adjusting parameters for said laser module;- an A / D converter module that receives an analog output of an analog feedback component and converts said analog output into digital laser data, said analog output being related to said laser output;- a DSP block that receives said digital laser data and processes said digital laser data to produce processed digital laser data;- a D / A converter module that receives processed digital laser data from said DSP block and converts said processed digital laser data into analog signals for said at least one control module;wherein said parameters used by said at least one control module to control said laser output are based on said analog signals.

[0012] In another aspect, the device further comprises an I / O module that cooperates with said DSP block to interface with a data processing device such that user input is used to adjust parameters for said laser output.

[0013] In yet a further aspect, the DSP block automatically operates to adjust said digital laser data such that said laser output is stabilized to a frequency or wavelength output that is related to a known result of an interaction between a reference element in said reference block and laser light of said laser output.

[0014] For the reference block, the reference element may be any one of: rubidium, cesium, iodine, sodium, potassium, thallium, and indium.

[0015] In another aspect, the parameters for said laser output adjusted by user input is one or more of: output frequency; output wavelength; output amplitude; output phase; output polarization; and a duration for a specific parameter setting.

[0016] In a further aspect, the device further comprises a laser power amplifier for amplifying an output of said laser module. For the device, the A / D converter module may comprise a photodiode that receives said analog output of saidAttorney Docket No. 1805P001W001reference block, an output of said photodiode being converted into said digital laser data.

[0017] In yet another aspect, the laser output is coupled to said reference block by way of a fiber optic medium. As well, in another alternative, the reference block is integrated into said device.

[0018] In a further aspect, the present invention further comprises at least one of: at least one SDR transceiver; and RF capable components. The at least one SDR transceiver and the RF capable components are controllable by software operated by a central control system that includes the at least one control module.

[0019] As a further aspect, analog signals and laser digital data representing analog signals are phase coherent such that signals and algorithms using such signals are combinable.

[0020] In yet a further aspect, the DSP block automatically operates to adjust said digital laser data such that said laser output is stabilized to a frequency or wavelength output that is related to a known result of an interaction between said reference block and laser light of said laser output. The interaction between said reference block and said laser light produces a measurable optical change in said laser light such that said measurable optical change is detectable by said A / D converter module.

[0021] In a further aspect, the FO module is operable to provide at least one of: low- level extensibility and high-level extensibility. This may include allowing for the addition of more ADC / DAC modules to add extra modulators as well as allowing for interfacing with Ethernet capable systems and devices.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The embodiments of the present invention will now be described by reference to the following figures, in which identical reference numerals in different figures indicate identical elements and in which:Attorney Docket No. 1805P001W001FIGURE 1 is a block diagram of one aspect of the present invention; andFIGURE 2A is another block diagram of another aspect of the present invention and which details some functions of the components;FIGURES 2B - 2G illustrate different configurations of the DSP block / processing unit that may be used in the device in Fig. 2A and in the different systems shown in Figs. 3 - 6;FIGURE 3 is a block diagram illustrating one enhancement of one aspect of the present invention;FIGURE 4 illustrates a block diagram of a further enhancement of the system illustrated in Fig. 3;FIGURE 5 shows a different enhancement of one aspect of the present invention; andFIGURE 6 shows yet a further configuration of one aspect of the present invention.DETAILED DESCRIPTION

[0023] Referring to Fig. 1, a block diagram of a laser system according to one aspect of the present invention is illustrated. As can be seen, this implementation of a device 10 according to one aspect of the present invention includes an A / D converter block 20 that includes a photodiode 30, a DSP module 40, a D / A converter block 50, a laser module 60 that is controlled by a temperature control block 70, and a current control block 80. A reference block 90 is coupled with fiber optics 100 to the laser output of the laser module 60.

[0024] In operation, the temperature control block 70 and the current control block 80 provide coarse and fine control over the laser output of the laser module 60. These control blocks receive analog signals from the D / A converter block 50 and, based on these analog signals, the control blocks adjust the laser output. It shouldAttorney Docket No. 1805P001W001be clear that these analog signals are converted into analog from digital laser data received by the D / A converter block 50 from the DSP module 40.

[0025] For clarity, the reference block receives the laser output from the laser module 60 by way of the fiber optics 100. The interaction between the contents of the reference block 90 and the laser output produces an optical output that is received from the reference block 90 by the photodiode 30. This optical output is then converted from an analog signal into digital laser data by the A / D converter block 20. The digital laser data is then passed to the DSP module 40 and processing is applied to the digital laser data to produce processed digital laser data. This processed digital laser data is what is sent to the D / A converter block 50.

[0026] Again for clarity, the term A / D converter block converts analog signals into digital signals while a D / A converter block converts digital signals into analog signals. As well, a DSP block performs digital signal processing (DSP) on digital data that it receives.

[0027] For clarity, the photodiode mentioned above and illustrated in Fig. 1 can represent more than one photodiode and, indeed, can represent multiple photodetector components. The optical output from the reference block can be, depending on the implementation and the desired use of the system, be received by one or more photodetectors. The output of the one or more photodetectors may then be further processed / combined to produce an analog signal that is converted into the digital laser data noted above.

[0028] Also for clarity, the reference block operates to provide a reference for the laser module such that the laser output is stabilized to a frequency / wavelength that is related to the content / element in the reference block. While there are many different ways to stabilize a laser, one method is to use a semiconductor diode laser and to stabilize it to a reference using a feedback / control loop. In one implementation, the feedback / control loop is provided by the laser module, the fiber optic lines, the reference block (that is fed the laser output from the laser module by the fiber optic lines), the A / D converter block (fed by the output from the reference block), and the DSP block and then the D / A control block. As can be seen from the figure and as explained above, the D / A control block's analogAttorney Docket No. 1805P001W001output is used to control the laser output. The feedback loop allows for the use of information from the laser’s interaction with the reference block to feed back to the laser’s temperature (slow coarse control) and driving current (fast precise control). Accordingly, if the laser output moves away from where it should be, this drift / change can be detected and corrected for by way of the DSP block. For greater clarity regarding stabilizing the laser output, stabilizing the laser output, in some schemes, may depend on generating an error signal between the actual laser output and the desired laser output. Once this error signal is obtained, then the laser output can be adjusted to reduce / minimize this error signal to eventually produce the stabilized laser output. Two known methods for generating the error signal are the “side of fringe locking” approach and the “FM spectroscopy” approach. Once the error signal is known (and hence what are the actual characteristics of your laser output), this information can then be used with a controller to minimize / eliminate the error signal. A Proportional-Integral- Differential (PID) control scheme may be used (in conjunction with the feedback loop noted above) to accomplish the laser output stabilization. Other approaches may, of course, be used as necessary.

[0029] It should be noted that the DSP block allows for the laser output to be adjusted.By adjusting and / or applying data processing to the laser data received from the A / D converter, the resulting laser output from the laser module can be changed as necessary. Among other properties, the output frequency, output wavelength, output amplitude, output phase, and output polarization of the laser output from the laser module can be adjusted / controlled. In addition, the duration for specific settings for specific parameters for the laser output can also be set by way of the DSP module.

[0030] To interface the device to a data processing system, an FO interface 300 may be present and may be coupled to the DSP module. The FO interface can exchange data with a suitably equipped data processing system (e.g., a PC, mobile phone, etc.) to allow a user to adjust laser output properties and / or behavior. If desired, based on user input, the laser output frequency, wavelength, polarization, phase, and amplitude can be set. These parameters can be set to specific values for a predetermined period of time and then changed to different specific values forAttorney Docket No. 1805P001W001another predetermined period of time. Or, alternatively, user input can set any one or any subset of these parameters to desired values as necessary.

[0031] As an alternative, while Fig. 1 shows the reference block as being external to the device, in some implementations, the reference block may be integrated into the device. For such an implementation, the reference block would be internal to the device and the range of frequencies and wavelengths for the laser output may be fixed as such frequencies and wavelengths would necessarily need to be related to the spectrum dictated by the element in the reference block. In other implementations, the reference block is external to the device and may be replaced. Such an implementation would allow for the device to be used with different reference blocks using different elements. This would allow for the generation of stabilized laser output of different ranges of wavelengths and frequencies. In another implementation, the device does not require a reference block with which to compare the laser output for frequency / wavelength stabilization. For such an implementation, temperature and / or current sensing components are used in place of the reference block in the feedback loop. The sensed temperature and / or current allows for the adjustment of the laser output such that the output is stabilized to a desired frequency / wavelength. In terms of implementation, the laser module may take the form of a module equipped with a suitable laser diode. Such modules can be found as commercial, off-the-shelf products that use diode lasers as distributed feedback lasers or external cavity diode lasers. Preferably, the laser module may be equipped with a low-noise laser diode (which may include internal optics) to simplify implementation. As well, instead of laser diodes, fiber lasers may be used. Similarly, modules that use external optical elements to adjust the characteristics of the laser output may be used with the laser module. Also in terms of implementation, the DSP module can be an FPGA (field programmable gate array), an ASIC, or even a general purpose CPU (with suitable programming). The DSP module can receive digital laser data and adjust / process this digital laser data as necessary or as instructed based on user input by way of the I / O interface. Thus, if specific digital laser data relates to a laser output's wavelength or frequency, this data can be adjusted such that the laser output will have a different wavelength or frequency as detailed by programming or by user input. Similarly, the DSPAttorney Docket No. 1805P001W001module can be programmed to change or adjust the laser output's parameters based on a time schedule or a duration. Again, this can be performed based on user input received through the I / O interface.

[0032] According to one implementation, the reference block may be a vapour cell with a specific element vapor inside. Clearly, as known by those of skill in the art, by comparing a laser output with the absorption spectrum of a vapor cell, the laser producing the laser output can be calibrated and this can ensure the laser's accuracy and stability. The vapor cell may be a rubidium cell, a cesium cell, an iodine cell, a sodium cell, a potassium cell, a thallium cell, an indium cell, or some other suitable vapor cell. As known to those of skill in the art, a different element used in the reference block would allow for different absorption spectra in the visible and near-infrared regions. Also as known to those of skill in the art, the vapor in the reference block can be an alkali metal (such as cesium, rubidium, sodium, or potassium), a halogen (such as iodine), or another element or compound (such as thallium, indium, or water). These vapors have characteristic absorption spectrums and, as such, the vapors absorb light at certain wavelengths and not others. By measuring the absorption of light by the vapor, one determines the wavelength or frequency of the laser output and, by using the feedback loop noted above, the wavelength or frequency of the laser output can be adjusted and locked to an appropriate value.

[0033] For greater clarity, the reference block need not be gas / vapour cells. The reference block can be spectroscopic references, interferometric references (such as Fabry-Perot, Mach-Zehnder, Michelson, etc.), or gas cells containing, e.g. iodine, oxygen, acetylene, methane, water, etc. As should be clear to a person of skill in the art, the selection of a reference block depends on the user’s desired wavelength and the precision of the stabilization. Depending on the implementation and the desired results, the reference block does not merely create amplitude changes (such as when the reference block is a gas / vapour cell) but can also change / adjust optical parameters for the feedback signal used by the photodiode / photodetector. Between the laser output received by the reference block and the optical output received by the photodiode / photodetector, the reference block introduces / creates a change in the laser properties, e.g.Attorney Docket No. 1805P001W001power / phase / polarization. This change, preferably, is for detection by the photodiode / photodetector.

[0034] It should be noted that the system of the present invention may include an optical amplifier to amplify laser output power. In one implementation, the amplifier may take the form of a semiconductor optical amplifier (SOA). Such an amplifier may be placed on a separate circuit board that interfaces with the main system.

[0035] Referring to Fig. 2A, a block diagram of the various functions of the device (and its component blocks and modules) according to one aspect of the present invention is illustrated. The reference numbers used in Fig. 2A correspond to the reference numbers used in Fig. 1 for similar components of the system according to another aspect of the present invention.

[0036] As can be seen from Fig. 2A, the laser module 60 (which may be a COTS laser such as DFB, ECDL, etc.) couples to the fibre network 100 such that the laser output is fed to the reference block 90. After the laser output interacts with the contents of the reference block, the output of the interaction is sent to the photodiode 30 and the photodiode’s output is converted by the A / D converter 20 into digital data (preferably at a high speed and with a high bit depth sampling). This digital data can then be processed by the DSP module 40. The DSP module can apply digital filters, generate error signals, allow forsignal / frequency / wavelength locking, or even apply FM spectroscopy to the digital data. Once the digital data has been processed, this processed digital data can then be converted into analog signals by the D / A converter block 50. In one implementation the D / A converter block has, for current feedback signals, a resolution in the Hz range and conversion speed of 100 MS / s while, for temperature feedback, may have a resolution in the uK range and a speed of IkS / s in terms of sampling rate. The analog signals are then used by the current 80 and temperature 70 controls to control the laser output. Of course, the processing by the DSP block 40 can be adjusted / controlled by user input by way of an VO interface (not illustrated). As can also be seen, the device has sufficient power regulation (by way of power regulation / power protection block 80A) and power input to power the various components along with controls (throughAttorney Docket No. 1805P001W001control block 80B) to provide any further control signals to the system. As well, in some implementations, telemetry from the device can be monitored to provide feedback to the user and to ensure that the device is operating within acceptable limits.

[0037] Referring to Figs. 2B-2G, illustrated are various configurations of the processing unit or DSP block 40 as shown in Fig. 2A. The various components in the processing unit / DSP block interface with the other components in the device 10. It should be clear that the device is quite flexible in terms of configurations and uses. The device can be used with different internal configurations and may be used in many contexts and with many external devices and subsystems.

[0038] Referring to Fig. 2B illustrated is one configuration of a DSP / processing unit. As can be seen, a control block 200 is present. The control block provides system control, telemetry control / handling, data logging, and handling the data logs. Also present is a temperature control loop block 210 that receives temperature data, processes that data, and outputs control signals for the temperature control 80. The DSP / processing unit may include one or more reconfigurable digital filters 220 that receives digital data from subsystems external to the DSP / processing unit. The filters 220 can then filter the incoming digital data to ensure only the necessary data is passed to the DSP / processing unit. Also present is an IQ demodulation block 230 that demodulates the signal coming from the digital filters. As is known, IQ demodulation separates the signal into its in-phase and quadrature components. As is known, the IQ demodulation block is used to isolate desired / relevant components from the received signal. For clarity, the IQ demodulation block 230 receives a signal from the digital filters 220 and from a direct digital synthesizer (DDS) 240. The synthesizer 240 synthesizes a digital signal and this signal is sent to either the IQ demodulation block 230 and to an open loop laser control block 250. Of course, the laser control block 250 outputs a control signal that is sent outside the DSP / processing unit to control the laser 60.

[0039] The output of the IQ demodulation block 230 is sent to a PID controller block 260 where the PID (proportional-integral-differentiator) controller provides control signals for, in this configuration, the laser. The PID block 260 output isAttorney Docket No. 1805P001W001then filtered by digital filters 270 and then sent to the laser control block 250. The configuration in Fig. 2B shows a lock-in amplifier locking regulator. This type of configuration is typical of a laser frequency-stabilization use case for the system.

[0040] The configuration in Fig. 2B can be extended to other frequency domains, e.g. the GHz domain by adding an SDR (software defined radio) topology RF transceiver 280 as shown in Fig. 2C. Due to the tight integration of the unit, the SDR data can be easily made coherent with the A / D converters or D / A converters of the core laser controller. The configuration of such a DSP / processing unit with the integrated RF transceiver is shown in Fig. 2C. As can be seen, the output of the DDS 240 is sent to the RF transceiver 280 and to the IQ demodulation block 230.

[0041] Referring to Fig. 2D, illustrated is another configuration for the DSP / processing unit. As can be seen, the configuration in the figure is very similar to that shown in Fig. 2C with the main difference being that the output of the DDS is sent to a component external to the DSP / processing unit. Additionally, there is no SDR RF transceiver in the configuration in Fig. 2D. If desired, the DDS signal could be provided by the user from an external source rather than generated in DDS (240) block. This external signal could be an analog signal delivered via the A / D interface, or a digital signal provided via the control block (200).

[0042] Yet another variant of the configuration in Fig. 2C is shown in Fig. 2E. As can be seen, the configuration in Fig. 2E also has an RF transceiver 280 that may receive signals from sources external to the DSP / processing unit. Additionally, other components that perform additional specific digital signal processing may be present in the additional DSP block 290. Such a block 290 may receive signals from, again, sources external to the DSP / processing unit.

[0043] Referring to Fig. 2F, illustrated is a different configuration for the DSP / processing unit for laser frequency stabilization. As can be seen, this configuration has similar components as the configuration in Fig. 2C. However, this configuration includes one or more PLL (phase locked loop) blocks 300 that are used to directly modulate the laser current at a given frequency. This frequency is stabilized to the received optical signal. Inside each PLL block 300 may be a DDS 310, another IQ demodulation block 320, and a PID (proportional-Attorney Docket No. 1805P001W001integral-differentiator) controller 330. In this configuration, the demodulation block 320 receives input from the outside of the DSP / processing unit and outputs the demodulated components of its input to the controller 330. The controller 330 sends its output to the DDS 310. The DDS 310 synthesizes a frequency and sends this to the demodulation block 320 and to a combiner block 340. The combiner block 340 combines the output of the DDS 240 with the output of DDS 310 and sends the combined output to the laser control block 250.

[0044] Referring to Fig. 2G, as can be seen, this configuration is simply an extension of the configuration in Fig. 2F. For this configuration, an SDR topology RF transceiver 350 is added to extend the configuration’s capabilities into other frequency domains (such as the GHz frequency range). Much like the configurations explained above, the SDR data for this configuration can be easily made coherent with the A / D converters / D / A converters of the core laser controller.

[0045] Accordingly, in one aspect of the present invention, there is provided a single, highly integrated device which contains a laser, optical modulators, and other optical systems (e.g. optical references), and control electronics consisting of an FPGA, an embedded processor, A / D and D / A converters, and RF components such as oscillators, SDR transceivers, synthesizers, amplifiers etc. This system provides a core common hardware platform that can be re-programmed using the FPGA / processor to implement the desired laser / control requirements multiple quantum / atomic / spectroscopy applications .

[0046] In another aspect of the present invention, the system according to the various aspects of the present invention allows for the implementation of a flexible, reprogrammable, suite of electronics and optics that can be rapidly reprogrammed to change, update, or improve the system’s functionality. In one aspect, the system may be configured to use standard fibre -coupled optical components such as laser diodes, switches, phase, frequency and amplitude modulators, polarization, etc. Such standard components connected by fibreoptics allow for the swapping of components in a manner akin to “plug-and-play” such that capabilities are easily added or removed as desired. This capability is applicable for both individual features at a given laser wavelength (e.g. amplitudeAttorney Docket No. 1805P001W001or frequency control) and for the swapping between completely different laser wavelengths (e.g. easily swapping out the laser diode and components from a 1550 nm system for gas spectroscopy to 780 nm for Rubidium sensors, to 422nm for Strontium-ion systems).

[0047] Another capability of the present invention is the use of easily software reconfigurable electronics that are capable of driving the flexible optical output. For this, basic control functions, such as laser temperature and current, are under high-resolution digital control. Once this control is available, more complex digital signal processing algorithms (e.g. lock-in / phase sensitive detection, control and feedback looks, data acquisition, etc.) are implementable using the same system. The system can be expanded to thereby add more control functions to operate other optical modulators and devices. This can be implemented by way of adding more digital-to-analog converter electronics to the core digital controller (e.g., the addition of Software Defined Radio (SDR) transceivers to control modulators such as EOMs (electro-optic modulators) or AOMs (acoustooptic modulators)).

[0048] For clarity, most of these electronics and optics are controllable by way of on- device software. As such, the device according to the present invention is modifiable and reconfigurable and can be modified and reconfigured to address the needs of various industries such as quantum technologies. These and other technologies (e.g., spectroscopy) that may require precise control of laser light can therefore be served by a device whose flexibility allows for multiple uses and applications.

[0049] Accordingly, in another aspect of the present invention, the system may include a software defined radio transceiver and other RF components (e.g. DDSs, synthesizer ICs) to the core electronics of the system. Such additional components would be software controllable and may also be user controllable by way of the FO interface detailed above. As another aspect, the system may have all inputs / DSP results / outputs to be phase coherent. Such a measure allows for combining signals and for combining various signal processing algorithms, regardless of which part of the system the signals may originate from.Attorney Docket No. 1805P001W001

[0050] In another aspect, the present invention provides a centralized, coherent,processor that enables complex and interdependent digital control loops to be implemented, including those which rely on more than one input-output pair.

[0051] For greater clarity, the I / O interface detailed above may include methods and components that allow for the reception from and transmission to other more complex systems. This may include low-level extensibility (e.g., the addition of more A / D converter / D / A converter modules to add extra modulators) and high- level extensibility (e.g., the integration of Ethernet (or other protocol / technology) connectivity to thereby allow interoperability and interfacing with other Ethernet capable devices and systems).

[0052] In another aspect, the use of RF capable components and modules (such as SDR transceivers) allows for the detection of RF frequencies and, therefore, the implementation of digital control logic on such frequencies. This allows the enhanced system to implement techniques requiring this, such as Residual Amplitude Modulation (RAM) cancellation servos on frequency / phase modulators. With the ability for RF detection, the system allows for the monitoring and reduction (if not cancellation) of unwanted effects on secondary parameters that such modulators can cause (e.g. a frequency modulator creating a small unwanted amplitude modulation).

[0053] As can be seen, the system of the present invention brings all the different parts of its control subsystem under single central processor / control. Such centralized control simplifies control schemes for the various applications and technologies that the present invention may be used with.

[0054] In another aspect of the present invention, the system creates a platform technology: a common core which can be easily adapted to different applications by updating the digital software / firmware, or the specific laser and optical modulator arrangement.

[0055] Referring to Fig. 3 to Fig. 6, illustrated are block diagrams of various configurations of the system of the present invention as configured and operated for different desired results and uses.Attorney Docket No. 1805P001W001

[0056] In Fig. 3, the system illustrated is configured to provide a spectrally pure laser output of low noise / linewidth whose frequency can be precisely tuned as compared to the frequency reference. As can be seen, the GPIO block 300 corresponds to the I / O interface detailed above while the frequency reference block corresponds to the reference block noted above. As can be seen, the frequency modulator block 310 is controlled by the SDR / RF electronics block 280 that forms part of the core electronics. As can be imagined, the processing unit block in Fig. 3 corresponds to (and subsumes) the DSP block in Fig. 1 and operates as the centralized controller for the system as a whole. This processing unit also provides control signals and control instructions as necessary for the SDR / RF electronics block and for the D / A converter block. Of course, the D / A converter block provides control signals and input for the optical power modulator 320. For clarity, the components illustrated as being outside the box labeled CORE ELECTRONICS may still be integrated into the single enclosure illustrated in Fig. 1.

[0057] For clarity, in most implementations, the components detailed as being CORE ELECTRONICS in Fig. 3 are to be contained in a single device. Other components, such a reference block (depending on implementation and what type of reference block is used) may also be contained in the device. Of course, for some applications, the reference block would be external to a single device enclosure. Additionally, one or more modulators may also be included in the single device enclosure. However, for some applications, where the component is bulky and extensive (e.g. a Fabry-Perot resonator as in Fig. 5 or an enclosure for a nanoparticle as detailed for Fig. 6), such component(s) would not be incorporated into a single device enclosure.

[0058] Referring to Fig. 4, illustrated is a system that is an extension of the system shown in Fig. 3. As can be seen, the system in Fig. 4 enables the imprinting of frequency and amplitude components to the main laser output. From the Figure, as contrasted to Fig. 3, Fig. 4 adds an additional optical power modulator block along with an additional frequency modulator block, with both additional blocks being fed (in series) by the fiber optic network. These two additional blocks are controlled by the SDR / RF electronics that form part of the core electronics. AsAttorney Docket No. 1805P001W001can be seen, the SDR / RF block controls both of the frequency modulator blocks while the D / A converter block provides control and input to the two optical modulator blocks.

[0059] In one implementation, this configuration is used for cold-atom quantum sensors or quantum computers. Additional modulators may be added by way of the D / A converter block or by way of the GPIO block to thereby provide control for additional parameters such as laser polarization. As can be imagined, this configuration is quite flexible in its applicability.

[0060] Referring to Fig. 5, illustrated is a different enhancement / extension to the system in Fig. 1. As can be seen, only a single frequency modulator block 310 is used (and is fed by the laser) and no optical power modulator is present. Instead, a gas sample in a Fabry-Perot resonator 400 is fed by the single frequency modulator and the outputs of the resonator are received by two optical detectors 410, 420 and by the photodetector 30 in the core electronics 10.

[0061] The configuration in Fig. 5 allows for the simultaneously imprinting of MHz and GHz signals onto a laser, interacting the laser output with a gas to be measured, and performing phase sensitive detection at 3-4 different MHz / GHz frequencies simultaneously. This configuration may be used in many industries but may also be used to detect greenhouse gases.

[0062] Referring to Fig. 6, yet a further extension / enhancement of the system of the present invention is illustrated. As can be seen, compared to Fig. 3, the system only uses an optically levitated quantum nanoparticle 450 that is excited by the laser output and the output from the nanoparticle block is received by the photodetector. No external frequency modulators or optical power modulators are used in this configuration. As well, it can be seen that the SDR / RF block is not used and the D / A converter block is, again, not used. Depending on the application, these blocks may be turned off. For some applications, (e.g. accelerometers using diamond nanoparticles) this configuration is useful as these applications only need the core electronics as can be seen from the Figure.

[0063] As another aspect of the present invention, the device according to the present invention can be, at its most basic, configured as a simple datalogger to monitorAttorney Docket No. 1805P001W001and store data from the optical measurements and implement control algorithms using software. The presence of re-configurable hardware acceleration, for example by using an FPGA, enables much more complex control algorithms to be developed.

[0064] In one aspect, there is provided a laser system that includes a device that includes an A / D converter block, a photodiode, a DSP module, a D / A converter block, a laser module that is controlled by a temperature control block, and a current control block. Also included is a reference block that is coupled with fiber optics to the laser output of the laser module. The temperature control block and the current control block provide coarse and fine control over the laser output of the laser module. These control blocks receive analog signals from the D / A converter block and, based on these analog signals, the control blocks adjust the laser output. These analog signals are converted into analog from digital laser data received by the D / A converter block from the DSP module. The reference block receives the laser output from the laser module by way of the fiber optics. The interaction between the contents of the reference block and the laser output produces an optical output that is received from the reference block by the photodiode. This optical output is then converted from an analog signal into digital laser data by the A / D converter block. The digital laser data is then passed to the DSP module and processing is applied to the digital laser data to produce processed digital laser data. This processed digital laser data is what is sent to the D / A converter block. The photodiode can represent more than one photodiode and may be multiple photodetector components. The optical output from the reference block can be received by one or more photodetectors. The output of the one or more photodetectors may then be further processed and / or combined to produce an analog signal that is converted into the digital laser. The reference block operates to provide a reference for the laser module such that the laser output is stabilized to a frequency / wavelength that is related to the content / element in the reference block. Laser stabilization may be implemented using a semiconductor diode laser and to stabilize it to a reference using a feedback / control loop. The feedback / control loop is provided by the laser module, the fiber optic lines, the reference block (that is fed the laser output from the laser module by the fiber optic lines), the A / D converter block (fed by theAttorney Docket No. 1805P001W001output from the reference block), and the DSP block and then the D / A control block. The D / A control block's analog output is used to control the laser output. The feedback loop allows for the use of information from the laser’s interaction with the reference block to feed back to the laser’s temperature (slow coarse control) and driving current (fast precise control). If the laser output moves away from where it should be, this drift / change can be detected and corrected for by way of the DSP block. Regarding stabilizing the laser output, stabilizing the laser output may depend on generating an error signal between the actual laser output and the desired laser output. Once this error signal is obtained, then the laser output can be adjusted to reduce / minimize this error signal to eventually produce the stabilized laser output. Generating the error signal may be implemented using either the “side of fringe locking” approach or the “FM spectroscopy” approach. Once the error signal is known (and hence what are the actual characteristics of the laser output), this information is used with a controller to minimize / eliminate the error signal. A Proportional-Integral-Differential (PID) control scheme, in conjunction with the feedback loop, to accomplish the laser output stabilization.

[0065] The DSP block allows for the laser output to be adjusted. By adjusting and / or applying data processing to the laser data received from the A / D converter, the resulting laser output from the laser module can be changed. Among other properties, the output frequency, output wavelength, output amplitude, output phase, and output polarization of the laser output from the laser module can be adjusted or controlled. In addition, the duration for specific settings for specific parameters for the laser output can also be set by way of the DSP module. To interface the device to a data processing system, an I / O interface may be used and may be coupled to the DSP module. The I / O interface exchanges data with a data processing system (e.g., a PC, mobile phone, etc.) and allows a user to adjust laser output properties and / or behavior. Based on user input, the laser output frequency, wavelength, polarization, phase, and amplitude can be set using the I / O interface. These parameters can be set to specific values for a predetermined period of time and then changed to different specific values for another predetermined period of time. The user input can set any one or any subset of these parameters to desired values as necessary.Attorney Docket No. 1805P001W001

[0066] The reference block may be external to the device or it may be integrated into the device. When the reference block is internal to the device, the range of frequencies and wavelengths for the laser output may be fixed as such frequencies and wavelengths would need to be related to the spectrum dictated by the element in the reference block. When the reference block is external to the device, the reference block may be replaced by different reference blocks using different elements. Using other reference blocks, stabilized laser output of different ranges of wavelengths and frequencies can be generated. When the reference block is omitted, temperature and / or current sensing components are used in place of the reference block in the feedback loop. The sensed temperature and / or current is used to adjust the laser output such that the output is stabilized to a desired frequency / wavelength. The laser module may take the form of a module equipped with a suitable laser diode. Such modules can be found as commercial, off-the-shelf products that use diode lasers as distributed feedback lasers or external cavity diode lasers. The laser module may be equipped with a low-noise laser diode (which may include internal optics) to simplify implementation or the laser module may use fiber lasers. The laser module may operate with / be used with modules that use external optical elements to adjust the characteristics of the laser output. The DSP module can be an FPGA (field programmable gate array), an ASIC, or even a general purpose CPU (with suitable programming). The DSP module can receive digital laser data and adjust orprocess this digital laser data as necessary or as instructed based on user input by way of the I / O interface. If specific digital laser data relates to a laser output's wavelength or frequency, the digital laser data can be adjusted such that the laser output will have a different wavelength or frequency as detailed by programming or by user input. Similarly, the DSP module can be programmed to change or adjust the laser output's parameters based on a time schedule or a duration of time. Again, this can be performed based on user input received through the I / O interface.

[0067] The reference block may be a vapour cell with a specific element vapor inside.By comparing a laser output with the absorption spectrum of a vapor cell, the laser producing the laser output can be calibrated and this ensures the laser's accuracy and stability. The vapor cell may be a rubidium cell, a cesium cell, anAttorney Docket No. 1805P001W001iodine cell, a sodium cell, a potassium cell, a thallium cell, an indium cell, or some other suitable vapor cell. A different element used in the reference block would allow for different absorption spectra in the visible and near-infrared regions. Also as known to those of skill in the art, the vapor in the reference block can be an alkali metal (such as cesium, rubidium, sodium, or potassium), a halogen (such as iodine), or another element or compound (such as thallium, indium, or water). These vapors have characteristic absorption spectrums and, as such, the vapors absorb light at certain wavelengths and not others. The device may operate by measuring the absorption of light by the vapor, and may determine the wavelength or frequency of the laser output. By using the feedback loop noted above, the wavelength or frequency of the laser output can be adjusted and locked to an appropriate value.

[0068] The reference block may use spectroscopic references, interferometric references (such as Fabry-Perot, Mach-Zehnder, Michelson, etc.), or gas cells containing, e.g. iodine, oxygen, acetylene, methane, water, etc. The selection of a reference block depends on the user’s desired wavelength and the precision of the stabilization. The reference block can also change / adjust optical parameters for the feedback signal used by the photodiode / photodetector. Between the laser output received by the reference block and the optical output received by the photodiode / photodetector, the reference block introduces / creates a change in the laser properties such as power, phase, or polarization. This change is for detection by the photodiode / photodetector.

[0069] The device may include an optical amplifier to amplify laser output power. The amplifier may be a semiconductor optical amplifier (SOA). Such an amplifier may be placed on a separate circuit board that interfaces with the main system.

[0070] The DSP / processing unit may include a control block (which provides system control, telemetry control / handling, data logging, data log handling). The DSP / processing unit also includes a temperature control loop block that receives temperature data, processes that data, and outputs control signals for the temperature control block. The DSP / processing unit may include one or more reconfigurable digital filters that receive digital data from other subsystems external to the DSP / processing unit. Also present in the DSP / processing unit isAttorney Docket No. 1805P001W001an IQ demodulation block that demodulates the signal coming from the digital filters. IQ demodulation separates the signal into its in-phase and quadrature components and thus isolates desired / relevant components from the received signal. Also included is a direct digital synthesizer (DDS) that synthesizes a digital signal and this signal is sent to either the IQ demodulation block or to an open loop laser control block. The IQ demodulation block output is sent to a PID controller block where the PID (proportional-integral-differentiator) controller provides control signals for the laser. The PID block output is filtered by digital filters and then sent to the laser control block. The DSP / processing unit may be configured as a lock-in amplifier locking regulator. The DSP / processing unit may include an SDR (software defined radio) RF transceiver.

[0071] The output of the DDS may be sent to a component external to the DSP / processing unit. The DDS signal could be provided by the user from an external source. This external signal could be an analog signal delivered via the A / D interface, or a digital signal provided via the control block.

[0072] The RF transceiver may receive signals from sources external to the DSP / processing unit. Other components that perform additional specific digital signal processing may be present in the additional DSP block. The components for additional DSP may receive signals from sources external to the DSP / processing unit.

[0073] The DSP / processing unit may include one or more PLL (phase locked loop) blocks that directly modulate the laser current at a given frequency. This frequency is stabilized to the received optical signal. The PLL block may include a DDS, an IQ demodulation block, and a PID (proportional-integral- differentiator) controller. In the PLL block, the demodulation block receives input from the outside of the DSP / processing unit and outputs the demodulated components of its input to the controller. The controller sends its output to the DDS. The DDS synthesizes a frequency and sends this to the demodulation block and to a combiner block. The combiner block combines the output of the DDS with the output of DDS and sends the combined output to the laser control block. The DSP / processing unit may include an RF transceiver.Attorney Docket No. 1805P001W001

[0074] The single, highly integrated device may include a laser, optical modulators, and other optical systems (e.g. optical references), and control electronics consisting of an FPGA, an embedded processor, A / D and D / A converters, and RF components such as oscillators, SDR transceivers, synthesizers, amplifiers etc. This system provides a core common hardware platform that can be reprogrammed using the FPGA / processor to implement the desired laser / control requirements multiple quantum / atomic / spectroscopy applications.

[0075] The system is a flexible, reprogrammable, suite of electronics and optics for rapidly re-programming to change, update, or improve the system’s functionality. The system may use standard fibre-coupled optical components such as laser diodes, switches, phase, frequency and amplitude modulators, polarization, etc. The components are connected by fibre-optics allow for the swapping of components in a manner similar to “plug-and-play” and capabilities are easily added or removed as desired. The system allows for control of individual features at a given laser wavelength (e.g. amplitude or frequency control) and for swapping between completely different laser wavelengths (e.g. easily swapping out the laser diode and components from a 1550 nm system for gas spectroscopy to 780 nm for Rubidium sensors, to 422nm for Strontium-ion systems).

[0076] Another capability of the present invention is the use of easily software reconfigurable electronics that are capable of driving the flexible optical output. For this, basic control functions, such as laser temperature and current, are under high-resolution digital control. Once this control is available, more complex digital signal processing algorithms (e.g. lock-in / phase sensitive detection, control and feedback looks, data acquisition, etc.) are implementable using the same system. The system can be expanded to thereby add more control functions to operate other optical modulators and devices. This can be implemented by way of adding more digital-to-analog converter electronics to the core digital controller (e.g., the addition of Software Defined Radio (SDR) transceivers to control modulators such as EOMs (electro-optic modulators) or AOMs (acoustooptic modulators)).

[0077] The electronics and optics in or working with the device are controllable by way of on-device software. The device is modifiable and reconfigurable to addressAttorney Docket No. 1805P001W001the needs of various industries such as quantum technologies. The device allows for precise control of laser light.

[0078] The device may include a software defined radio transceiver and other RF components (e.g. DDSs, synthesizer ICs). These components are software controllable and may also be user controllable by way of the I / O interface. The device may have all inputs / DSP results / outputs to be phase coherent. This phase coherence allows for combining signals and for combining various signal processing algorithms, regardless of which part of the system the signals may originate from.

[0079] RF capable components and modules (such as SDR transceivers) in the device allows for the detection of RF frequencies and implementation of digital control logic on such frequencies. The device can implement Residual Amplitude Modulation (RAM) cancellation servos on frequency / phase modulators. The device can monitor and reduce (if not cancel) unwanted effects on secondary parameters that such modulators can cause (e.g. a frequency modulator creating a small unwanted amplitude modulation).

[0080] A person understanding this invention may now conceive of alternative structures and embodiments or variations of the above all of which are intended to fall within the scope of the invention as defined in the claims that follow.

Claims

Attorney Docket No. 1805P001W001We claim:

1. A device for producing a laser output, the device comprising:- a laser module producing said laser output;- at least one control module that controls said laser output by adjusting parameters for said laser module by way of at least one or more of: current control and temperature control;- an A / D converter module that receives an analog output of a reference block after said laser output has interacted with said reference block and that converts said analog output into digital laser data;- a DSP block that receives said digital laser data and processes said digital laser data to produce processed digital laser data;- a D / A converter module that receives processed digital laser data from said DSP block and converts said processed digital laser data into analog signals for said at least one control module;wherein said parameters used by said at least one control module to control said laser output are based on said analog signals.

2. The device according to claim 1, further comprising an I / O module that cooperates with said DSP block to interface with a data processing device such that user input is used to adjust parameters for said laser output.

3. The device according to claim 1, wherein said DSP block automatically operates to adjust said digital laser data such that said laser output is stabilized to a frequency or wavelength output that is related to a known result of an interaction between a reference element in said reference block and laser light of said laser output.

4. The device according to claim 3, wherein said reference element is any one of: rubidium, cesium, iodine, sodium, potassium, thallium, and indium.

5. The device according to claim 2, wherein parameters for said laser output adjusted by user input is one or more of:Attorney Docket No. 1805P001W001- output frequency;- output wavelength;- output amplitude;- output phase;- output polarization; and- a duration for a specific parameter setting.

6. The device according to claim 1, further comprising a laser power amplifier for amplifying an output of said laser module.

7. The device according to claim 1, wherein said A / D converter module comprises a photodiode that receives said analog output of said reference block, an output of said photodiode being converted into said digital laser data.

8. The device according to claim 1, wherein said laser output is coupled to said reference block by way of a fiber optic medium.

9. The device according to claim 1, wherein said reference block is integrated into said device.

10. A device for producing a laser output, the device comprising:- a laser module producing said laser output;- at least one control module that controls said laser output by adjusting parameters for said laser module;- an A / D converter module that receives an analog output of an analog feedback component and converts said analog output into digital laser data, said analog output being related to said laser output;- a DSP block that receives said digital laser data and processes said digital laser data to produce processed digital laser data;- a D / A converter module that receives processed digital laser data from said DSP block and converts said processed digital laser data into analog signals for said at least one control module;Attorney Docket No. 1805P001W001wherein said parameters used by said at least one control module to control said laser output are based on said analog signals.

11. The device according to claim 10, wherein said analog feedback component measures at least one of: temperature and current for said laser module.

12. The device according to claim 10, further comprising an I / O module that cooperates with said DSP block to interface with a data processing device such that user input is used to adjust parameters for said laser output.

13. The device according to claim 12, wherein parameters for said laser output adjusted by user input is one or more of:- output frequency;- output wavelength;- output amplitude;- output phase;- output polarization; and- a duration for a specific parameter setting.

14. The device according to claim 1, further comprising at least one of:- at least one SDR transceiver; and- RF capable components.

15. The device according to claim 14, wherein said at least one SDR transceiver and said RF capable components are controllable by software operated by a central control system that includes said at least one control module.

16. The device according to claim 1, wherein analog signals and laser digital data representing analog signals are phase coherent such that said signals are combinable.

17. The device according to claim 12, wherein said I / O module is operable to provide at least one of: low-level extensibility and high level extensibility.Attorney Docket No. 1805P001W00118. The device according to claim 1, wherein said DSP block automatically operates to adjust said digital laser data such that said laser output is stabilized to a frequency or wavelength output that is related to a known result of an interaction between said reference block and laser light of said laser output.

19. The device according to claim 18, wherein said interaction between said reference block and said laser light produces a measurable optical change in said laser light such that said measurable optical change is detectable by said A / D converter module.

Images