Optical intensity modulation device and laser system

Abstract

an optical intensity modulation device (100) comprising: an optical modulator (102) operative to modulate a continuous wave optical carrier signal at a carrier wavelength to generate one or more sidebands on the optical carrier signal; a radio frequency (RF) signal generator (104) operative to provide an RF drive signal to the optical modulator; a first optical waveguide grating (108) having a center reflection wavelength corresponding to the sidebands; and an optical circulator (106) configured to direct the optical carrier signal and the one or more sidebands into the first optical waveguide grating and to direct a reflected optical signal from the first optical waveguide grating towards an output to form an output optical signal, wherein the RF signal generator is operative to switch the drive signal on and off to form an intensity modulated output optical signal.

Description

[Technical Field]

[0001] The present invention relates to an optical intensity modulation device. The present invention further relates to a laser system comprising an optical intensity modulation device. The present invention further relates to a system for coherent excitation. The present invention further relates to a quantum computing system. The present invention further relates to a system for coherent state control of a quantum system. [Background technology]

[0002] High-speed optical intensity modulation of optical signals is typically performed using acousto-optic modulators (AOMs), Mach-Zehnder electro-optic modulators (MZM-EOMs), or semiconductor optical amplifiers (SOAs). AOMs have high extinction ratios, and intensity modulation can be controlled to avoid generating phase shifts in the optical signal (this can be called "phase / amplitude coupling"). However, they have slow rise times, which means that AOMs are not suitable for ultrafast intensity modulation. MZM-EOMs have fast rise times but low extinction ratios, meaning they are not suitable for applications requiring amplification of pulse trains with long dark periods. They generate phase / amplitude coupling, meaning they are not suitable for applications requiring precise phase control of optical signals. SOAs have high extinction ratios, rise times significantly faster than AOMs but slower than MZM-EOMs, and generate phase / amplitude coupling. Summary of the Invention [Problem to be solved by the invention]

[0003] An object is to provide an improved optical intensity modulation apparatus. A further object is to provide an improved laser system. A further object is to provide an improved system for coherent excitation. A further object is to provide an improved system for optical quantum computing. A further object is to provide an improved apparatus for coherent state control of quantum systems. [Means for solving the problem]

[0004] One aspect provides an optical intensity modulation device comprising an optical modulator, a radio frequency (RF) signal generator, a first optical waveguide grating, and an optical routing device. The optical modulator operates to modulate a continuous wave (cw) optical carrier signal at a carrier wavelength to generate one or more sidebands on the optical carrier signal. The one or more sidebands may be first-order sidebands, such as upper or lower sidebands from the carrier wavelength. The modulated signal output from the modulator may include multiple higher-order sidebands. The RF signal generator operates to provide an RF drive signal to the optical modulator. The first optical waveguide grating preferably has a center reflection wavelength corresponding to the sidebands. The waveguide grating may further have a reflection bandwidth selected so as not to overlap with the carrier signal, i.e., the bandwidth is equal to or less than the frequency offset of the sidebands relative to the carrier signal. The reflection bandwidth may be defined as a full width at half maximum (FWHM). The optical routing device is configured to direct the optical carrier signal and one or more sidebands to a first optical waveguide grating and direct a reflected optical signal from the first optical waveguide grating toward an output to form an output optical signal, and the RF signal generator is operative to switch a drive signal on and off to form an intensity-modulated output optical signal.

[0005] An optical intensity modulator may provide a high extinction ratio (ER), fast rise time (RT) and / or fall time (FT), and independent phase and amplitude control of optical pulses. Preferably, the optical intensity modulator is configured so that there is no coupling between the imposed phase and amplitude. Many quantum systems, such as quantum computers, atomic clocks, and atomic interferometers, require unique amplitude-shaped pulses and perfect control of the optical phase. Furthermore, a high extinction ratio is required for energy-efficient amplification of pulse trains with long dark periods. The extinction ratio may be understood to have its general meaning in the art. One definition is that the extinction ratio is the ratio of the optical power level generated when the modulator is open to the power level generated when the modulator is closed. It may be expressed as a fraction, in dB, or as a percentage. The optical intensity modulator may provide improvements in the above-mentioned parameters compared to the AOM, MZ-EOM, and SOA mentioned above. As an example, the optical intensity modulator may have an extinction ratio greater than 30 dB, such as greater than 40 dB, such as 50 dB or greater. The rise time of the device can be extremely fast, such as a rise time of less than 1 ns, or less than 500 ps, ​​or even less than 100 ps. Rise time can be understood as the time between 10% and 90% signal, for example in terms of power or detected voltage.

[0006] In one embodiment, the first optical waveguide grating is a first fiber Bragg grating. In one embodiment, the first fiber Bragg grating is an apodized fiber Bragg grating with a ridged Gaussian reflection profile and a constant grating period, which can provide very good sidelobe suppression and a sharp reflection profile, making the first FBG suitable for separating signals that are closely spaced in frequency.

[0007] In one embodiment, the optical routing device is an optical circulator. In one embodiment, the optical modulation device further comprises an output optical waveguide grating provided after the optical routing device, i.e., between the optical routing device and the output of the optical intensity modulation device. The output optical waveguide grating may have a reflection bandwidth that includes the carrier wavelength. The output optical waveguide grating may further improve the extinction ratio of the optical modulation device by further suppressing the optical carrier signal.

[0008] Preferably, there is substantially no reflection of the optical carrier signal or any other generated sidebands other than said sidebands from the first optical waveguide grating back to the optical routing device. The sidebands of interest may be first-order sidebands adjacent to the carrier signal, for example, upper or lower sidebands on either side of the carrier signal. In one embodiment, the optical modulator and optical routing device are disposed along a first optical path, and the optical routing device and the first optical waveguide grating are disposed along a second optical path, which does not include an optical waveguide grating having a central reflection wavelength corresponding to the carrier signal or other generated sidebands other than the sidebands. The optical carrier signal and other generated sidebands are then transmitted by the first optical waveguide grating to, for example, an optical dump at the end of the second optical path. An output optical signal is thereby output only when the optical modulator generates the sidebands. The optical dump may comprise or include an optical isolator. Alternatively, other fiber cable terminations, such as fiber pigtails or anti-reflection coated fiber end caps, may be used.

[0009] In one embodiment, the first optical path does not include any optical waveguide gratings other than the first optical waveguide grating. In one embodiment, the first optical waveguide grating may be disposed in a first optical waveguide that is free of any optical waveguide grating having a center reflection wavelength corresponding to any other generated sideband other than the sideband, such as a carrier signal or any other optical waveguide grating other than the first optical waveguide grating.

[0010] Preferably, any reflection of the optical carrier signal in the first optical waveguide towards the output is less than 10%, such as less than 1%, such as less than 2%, such as less than 5%, of the optical carrier signal guided in the first optical waveguide grating.

[0011] In one embodiment, the output optical waveguide grating is a further Bragg grating. In one embodiment, the optical modulation device further comprises a second optical waveguide grating and a second optical routing device. The second optical waveguide grating has a center reflection wavelength corresponding to the sideband. The second optical routing device is configured to direct the reflected optical signal from the first optical waveguide grating to the second optical waveguide grating and to direct the second reflected optical signal from the second optical waveguide grating toward the output. The second optical waveguide grating may further improve the extinction ratio of the optical modulation device.

[0012] In one embodiment, the second optical waveguide grating is a second fiber Bragg grating. In one embodiment, the second fiber Bragg grating is an apodized fiber Bragg grating with a raised Gaussian reflection profile and a constant grating period, which can enable very good sidelobe suppression and a sharp reflection profile, making the second FBG suitable for separating signals that are closely spaced in frequency.

[0013] In one embodiment, the second optical routing device is a second optical circulator. In one embodiment, the optical modulation device further comprises an output optical waveguide grating provided after the second optical routing device. The output optical waveguide grating may have a reflection bandwidth that includes the carrier wavelength. The output optical waveguide grating may further suppress the optical carrier signal, thereby further improving the extinction ratio of the optical modulation device.

[0014] In one embodiment, the output optical waveguide grating is a further fiber Bragg grating. In one embodiment, the optical modulator operates to modulate the cw optical carrier signal to generate a lower sideband and an upper sideband on the optical carrier signal. The first optical waveguide grating has a center reflection wavelength corresponding to one of the lower sideband and the upper sideband. The optical modulator may operate to modulate the cw optical carrier signal to generate only the lower sideband and the upper sideband on the optical carrier signal, but not to generate additional sidebands. This is advantageous over devices that generate additional sidebands because the optical power of the modulated carrier signal is maintained in only two sidebands, rather than being distributed across several sidebands.

[0015] In one embodiment, the output optical waveguide grating has a reflection bandwidth that includes the carrier wavelength and the other of the upper sideband or the lower sideband, and may further improve the extinction ratio of the optical modulator by further suppressing the optical carrier signal and the other of the upper sideband or the lower sideband.

[0016] In an alternative embodiment, the optical modulator is a single-sideband (SSB) modulator that operates to modulate the cw optical carrier signal to generate a single sideband on the optical carrier signal. The optical modulator may operate to modulate the cw optical carrier signal to generate only a single sideband on the optical carrier signal and not generate additional sidebands. This is advantageous over devices that generate two or more additional sidebands because the optical power of the modulated carrier signal is maintained in only a single sideband rather than being distributed across several sidebands. In some embodiments, the optical modulator includes a serrodyne modulator. The first optical waveguide grating has a center reflection wavelength corresponding to the generated sideband.

[0017] In one embodiment, the RF signal has a frequency up to 100 GHz, such as a frequency in the range of 1 GHz to 20 GHz. The first optical waveguide grating may have a reflection bandwidth less than or equal to the frequency of the RF drive signal.

[0018] Corresponding embodiments and advantages apply to the laser systems, quantum computing systems, and systems for coherent excitation described below. In one embodiment, an RF signal generator operates to provide an RF drive signal including an RF signal pulse having a compensation pulse shape such that one or more sidebands include an optical pulse having the compensation pulse shape. The compensation pulse shape is configured to compensate for the non-uniform gain response of the optical amplifier in the time domain. Thus, an optical modulator may be used to deliver preformed optical pulses to the optical amplifier, enabling pulses of a desired pulse shape to be output from the optical amplifier. Figures 17-18 show examples of preformed optical pulses and optical pulses output from the optical amplifier, respectively. The shape of the optical pulses may be controlled by controlling or modulating the amplitude of the RF drive signal. Thus, amplitude modulation of the optical signal may correspond to amplitude modulation of the RF drive signal.

[0019] One aspect provides a laser system including a light source and an optical intensity modulation device. The light source is preferably configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength. The light source may be a laser, such as a single-frequency fiber laser. In some embodiments, the carrier wavelength is in the range of about 1500 nm to about 1600 nm, such as 1540 nm to 1580 nm. Preferably, the light source provides an optical carrier signal with a long coherence length so that the phase of the signal is well-defined over long periods of time. The optical intensity modulation device includes an optical modulator, a radio frequency (RF) signal generator, a first optical waveguide grating, and an optical routing device. The optical modulator operates to modulate the continuous wave (cw) optical carrier signal at the carrier wavelength to generate one or more sidebands on the optical carrier signal. The RF signal generator operates to provide an RF drive signal to the optical modulator. The first optical waveguide grating has a center reflection wavelength corresponding to the sidebands. The optical routing device is configured to direct the optical carrier signal and one or more sidebands to a first optical waveguide grating and direct a reflected optical signal from the first optical waveguide grating toward an output to form an output optical signal. The RF signal generator operates to switch a drive signal on and off to form an intensity-modulated output optical signal. The components may be arranged as described below. The output of the light source may be used as an input to an optical modulator. The RF signal generator may provide an RF drive signal to the optical modulator. The modulated signal output from the modulator may be input to the optical routing device, which may direct the signal to a first optical waveguide grating configured to reflect a center reflected wavelength. The reflected wavelength from the grating may be input to an optical amplifier via the optical routing device. An exemplary embodiment is shown in FIG. 9.

[0020] In one embodiment, the RF signal generator operates to provide an RF drive signal including an RF signal pulse having a compensation pulse shape such that one or more sidebands include an optical pulse having the compensation pulse shape. The compensation pulse shape is configured to compensate for the non-uniform gain response of the optical amplifier in the time domain. Thus, a laser may be used to deliver pre-shaped optical pulses to the optical amplifier, enabling pulses of a desired pulse shape to be output from the optical amplifier. In some embodiments, the compensation or pre-shaped optical pulses have an exponential envelope in amplitude or intensity such that the desired pulse shape output from the optical amplifier is approximately rectangular in the time domain. This may be achieved by utilizing an amplitude-modulated RF drive signal having an exponential envelope. An example of a pre-shaped optical pulse is shown in FIG. 17. An example of a desired pulse shape output from the optical amplifier is shown in FIG. 18.

[0021] In an alternative embodiment, the optical intensity modulation device further comprises an optical amplifier and an optical detector. The optical amplifier is configured to amplify the intensity-modulated output optical signal from the optical intensity modulation device. The optical amplifier has a non-uniform gain response in the time domain. The optical detector is configured to detect the pulse shape of the intensity-modulated output optical signal after amplification by the optical amplifier and generate an output signal indicative of the detected pulse shape. The RF signal generator comprises an interface circuit, one or more processors, and a memory including instructions executable by the processor, whereby the RF signal generator operates as follows: Receive an output signal indicative of the detected pulse shape from the optical detector; Determine a difference between the detected pulse shape and a target pulse shape; Determine a compensation pulse shape configured to at least partially compensate for the difference; Generate an RF drive signal including an RF signal pulse having a compensation pulse shape such that one or more sidebands include an optical pulse having the compensation pulse shape. Thus, the optical modulation device may be used to deliver preformed optical pulses to the optical amplifier, enabling pulses of a desired pulse shape to be output from the optical amplifier. Thus, an output port, such as a third port, of the optical routing device may be connected to an input port of the optical amplifier via an optical fiber.

[0022] Corresponding embodiments also apply to quantum computing systems and systems for coherent excitation described below. One aspect provides a quantum computing system comprising a light source, an optical intensity modulation device, and a confinement chamber. The light source may be configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength. The optical intensity modulation device comprises an optical modulator, a radio frequency (RF) signal generator, a first optical waveguide grating, and an optical routing device. The optical modulator operates to modulate the continuous wave (cw) optical carrier signal at the carrier wavelength to generate one or more sidebands on the optical carrier signal. The RF signal generator operates to provide an RF drive signal to the optical modulator. The first optical waveguide grating has a center reflection wavelength corresponding to the sidebands. The optical routing device is configured to guide the optical carrier signal and the one or more sidebands to the first optical waveguide grating and direct a reflected optical signal from the first optical waveguide grating toward an output to form an output optical signal delivered to the confinement chamber. The RF signal generator operates to switch the drive signal on and off to form an intensity-modulated output optical signal.

[0023] One aspect provides a system for coherent pumping, comprising a light source, an optical intensity modulation device, and an excitation chamber. The light source may be configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength. The optical intensity modulation device comprises an optical modulator, a radio frequency (RF) signal generator, a first optical waveguide grating, and an optical routing device. The optical modulator operates to modulate the continuous wave (cw) optical carrier signal at the carrier wavelength to generate one or more sidebands on the optical carrier signal. The RF signal generator operates to provide an RF drive signal to the optical modulator. The first optical waveguide grating has a center reflection wavelength corresponding to the sidebands. The optical routing device is configured to direct the optical carrier signal and the one or more sidebands into the first optical waveguide grating and direct a reflected optical signal from the first optical waveguide grating toward an output to form an output optical signal delivered to the excitation chamber. The RF signal generator operates to switch the drive signal on and off to form an intensity-modulated output optical signal.

[0024] One aspect provides a system for coherent state control of a quantum system. The system includes a light source, an optical intensity modulation device, and an interaction chamber for the quantum system. The light source may be configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength. The optical intensity modulation device includes an optical modulator, a radio frequency (RF) signal generator, a first optical waveguide grating, and an optical routing device. The optical modulator operates to modulate the continuous wave (cw) optical carrier signal at the carrier wavelength to generate one or more sidebands on the optical carrier signal. The RF signal generator operates to provide an RF drive signal to the optical modulator. The first optical waveguide grating has a center reflection wavelength corresponding to the sidebands. The optical routing device is configured to guide the optical carrier signal and the one or more sidebands to the first optical waveguide grating and to direct a reflected optical signal from the first optical waveguide grating toward an output to form an output optical signal delivered to the interaction chamber. The RF signal generator operates to switch a drive signal on and off to form an intensity modulated output optical signal.

[0025] The disclosed optical intensity modulation devices and related laser systems may be used in many applications, particularly those requiring precise control of the phase, energy, and / or shape of the output optical signal. For example, many quantum applications require specific trains of optical pulses with well-defined shapes, phases, and energies. Examples of such applications include atomic, molecular, and optical physics (AMO), quantum computers, cryptography, quantum gyroscopes, gravity detection systems, and atomic clocks. The disclosed devices and systems enable state control of quantum mechanical ensembles. Other applications include distributed acoustic sensing. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a block diagram illustrating an embodiment of a light intensity modulation device. [Figure 2] FIG. 1 is a block diagram illustrating an embodiment of a light intensity modulation device. [Figure 3] FIG. 1 is a block diagram illustrating an embodiment of a light intensity modulation device. [Figure 4] FIG. 1 is a block diagram illustrating an embodiment of a light intensity modulation device. [Figure 5] FIG. 1 is a block diagram illustrating an embodiment of a light intensity modulation device. [Figure 6] FIG. 1 is a block diagram illustrating an embodiment of a light intensity modulation device. [Figure 7] FIG. 1 is a block diagram illustrating an embodiment of a light intensity modulation device. [Figure 8] FIG. 1 is a block diagram illustrating an embodiment of a laser system. [Figure 9] FIG. 1 is a block diagram illustrating an embodiment of a laser system. [Figure 10] FIG. 1 is a block diagram illustrating an embodiment of a laser system. [Figure 11] 1 is a block diagram illustrating an embodiment of a system for coherent excitation of atoms or ions. [Figure 12] FIG. 1 is a block diagram illustrating one embodiment of a quantum computing system. [Figure 13] FIG. 1 is a block diagram illustrating one embodiment of a system for coherent state control of quantum systems. [Figure 14] FIG. 1 is a block diagram illustrating an embodiment of a light intensity modulation device. [Figure 15] 10 is a graph showing experimental data (fall time) regarding the light intensity modulation device according to the present disclosure. [Figure 16] 10 is a graph showing experimental data (rise time) regarding the light intensity modulation device according to the present disclosure. [Figure 17] 1A and 1B are diagrams illustrating optical pulse shapes having a compensation pulse shape configured for a non-uniform gain response in the time domain of an optical amplifier. [Figure 18] 1 illustrates the shape of an optical pulse output from an optical amplifier having a non-uniform gain response in the time domain. [Figure 19] FIG. 2 is a graph showing the reflection spectrum of the first optical waveguide grating according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0027] Referring to FIG. 1, one embodiment provides an optical intensity modulation device 100 comprising an optical modulator 102, a radio frequency (RF) signal generator 104, a first optical waveguide grating 108, and an optical routing device 106.

[0028] The RF signal generator operates to provide an RF drive signal to the optical modulator. The optical modulator is disposed in the first optical path to receive a continuous wave (cw) optical carrier signal at a carrier wavelength. The optical modulator operates to modulate the optical carrier signal to generate one or more sidebands on the optical carrier signal. The one or more sidebands may have a frequency offset from the carrier signal corresponding to the frequency of the RF drive signal.

[0029] A first optical waveguide grating OWG 108 is disposed in the second optical path connecting the first optical waveguide grating to the optical routing device and has a center reflection wavelength corresponding to the sideband. The optical routing device 106 is configured to direct the optical carrier signal and one or more sidebands along a second optical path to a first optical waveguide grating. The optical routing device 106 is also configured to direct the optical signal reflected from the first optical waveguide grating along the second optical path toward a third optical path to an output to form an output optical signal. Because the optical waveguide having the first optical waveguide grating does not have a waveguide grating with a center reflection wavelength corresponding to the carrier wavelength, the carrier signal is not reflected toward the output, nor is a portion of the output optical signal reflected. Additionally, the optical waveguide does not have a grating with a center reflection wavelength corresponding to any other generated sidebands.

[0030] The RF signal generator operates to switch the drive signal on and off, such that when the drive signal is on, one or more sidebands are generated, and when the drive signal is off, no sidebands are generated. By switching the drive signal on and off, an intensity-modulated output optical signal is formed.

[0031] In one embodiment, the RF signal has a frequency up to 100 GHz, such as a frequency in the range of 1 GHz to 20 GHz. In one embodiment, the RF signal generator 104 is a high-speed arbitrary waveform generator (AWG).

[0032] In one embodiment shown in FIG. 2 , the optical modulator is an electro-optic modulator (EOM) 202, the first optical waveguide grating is a first fiber Bragg grating (FBG) 208, and the optical routing device is an optical circulator 206. Advantageously, the EOM may be configured to apply or impose phase modulation on the carrier signal. An advantage of utilizing phase modulation is that the setup is simpler than, for example, a Mach-Zehnder (MZ) modulator. In particular, with an MZ-EOM, precise control of the bias voltage is important, which makes the setup more complex. This is especially true for pulsed light applications, as it requires complex electronics. This is completely avoided by utilizing a phase-modulation-based EOM. Phase-modulation-based EOMs may be used in other embodiments described herein.

[0033] Alternatively, the optical modulator may be configured to apply or impose amplitude modulation on the carrier signal, and thus in some cases the carrier signal may be both amplitude and phase modulated by the optical modulator.

[0034] The RF signal generator operates to provide an RF drive signal to the EOM. The phase of the RF drive signal may have a known correlation with the phase of the optical carrier signal and / or the phase of one or more sidebands. In some embodiments, the phase of the RF signal does not affect the phase of the optical carrier signal. The phase of the optical signal in the first sideband may have a 1:1 correlation with the phase of the RF signal. In the second sideband, the phase of the optical signal may be 1:2 that of the RF signal. Thus, by controlling the phase of the RF drive signal, the phase of the optical signal may be controlled. The phase change relative to the optical carrier signal may be independent of the selection of the frequency of the RF drive signal.

[0035] The EOM is cThe EOM is configured to receive a cw optical carrier signal of wavelength λ . The EOM is driven by an RF drive signal from an RF signal generator 104 and phase modulates the cw optical carrier signal. The EOM modulates the optical carrier signal to phase modulate the optical carrier signal to produce an upper sideband wavelength λ . u The upper and lower sideband wavelengths λ l The RF drive signal operates to generate a lower sideband of . The RF drive signal is at frequency f, so that the sideband is spaced from the carrier wavelength by an optical frequency offset f. Advantageously, the corresponding wavelength offset between the carrier wavelength and a given first-order sideband corresponds approximately to the reflection bandwidth of the first optical waveguide grating. This allows for precise filtering of the sideband of interest while suppressing reflection of the carrier signal from the grating. In some embodiments, the reflection bandwidth of the first optical waveguide grating is less than 1 nm at a wavelength of 1560 nm. In other embodiments, the reflection bandwidth is between 10 pm and 100 pm at a wavelength of 1560 nm. This corresponds approximately to a bandwidth between 1.233 GHz and 12.33 GHz. Advantageously, the frequency of the RF drive signal is within the same range. In some embodiments, the first optical waveguide grating has a reflection bandwidth between 1 GHz and 10 GHz at the carrier wavelength.

[0036] The EOM may include a nonlinear optical material, such as a ferroelectric material like lithium niobate (LiNbO) or barium titanate (BaTiO), a polymer, an organic electro-optic material, or other suitable nonlinear material. In particular, the EOM may include a nonlinear crystal whose refractive index is a function of the strength of the local electric field. Thus, the refractive index of the crystal as well as the phase of the optical signal exiting the EOM may be controlled by varying the electric field in the crystal, for example, by controlling an RF drive signal generated by an RF signal generator.

[0037] The output of the EOM is connected to a first port 1 of an optical circulator by a first optical fiber 210. The optical circulator is configured to route the optical signal from the first port to a second port 2 to which a second optical fiber 212 containing a first FBG 208 is connected. Thus, the optical carrier signal, upper sideband, and lower sideband output from the EOM are guided by the optical circulator to the first FBG.

[0038] The first FBG 208 has a reflectivity profile that includes a central reflection wavelength corresponding to the upper sideband in this example. Depending on the reflectivity of the first FBG, a certain percentage of the upper sideband is reflected by the first FBG, which is typically in the range of 90% to 99%. The optical carrier signal and the lower sideband are transmitted by the first FBG toward an optical dump 214 at the end of the optical fiber. The optical dump 214 may include an optical isolator. The optical isolator may be configured to allow light to propagate through the isolator in one direction but not in the opposite direction. The operation of the optical isolator may be based on the Faraday effect. Depending on the reflectivity profile of the first FBG, a small percentage (e.g., 0.01% to 1%) of the optical carrier signal and the lower sideband may be reflected by the FBG.

[0039] The optical circulator 206 is configured to route the optical signal reflected from the first FBG from the second port 2 to the third port 3 to the output optical fiber 216 to form an output optical signal. The output optical signal from the optical circulator 206 may be provided as an input to an optical amplifier (not shown in this embodiment) via the output optical fiber 216.

[0040] Where an optical circulator is described as being used, it will be appreciated that a four-port optical coupler, preferably a 50:50 optical coupler, may alternatively be used. The RF signal generator operates by switching the drive signal on and off. When the drive signal is on, an upper sideband and a lower sideband are generated. When the drive signal is off, no sidebands are generated. In this example, when the drive signal is on, the upper sideband is present and is reflected by the first FBG and directed toward the output as an output optical signal. By switching the drive signal on and off, an intensity-modulated output optical signal at the upper sideband wavelength is formed.

[0041] In one embodiment, the first FBG 208 is an apodized FBG with a ridged Gaussian reflection profile and a constant grating period. The first FBG 208 may be mounted on an aluminum substrate with a temperature sensor and a piezoelectric actuator to control and stabilize its central reflection wavelength. Alternatively, the first FBG 208 may be mounted on a ceramic substrate. In this case, temperature can be stabilized without the use of a piezoelectric actuator.

[0042] In one embodiment shown in FIG. 3, the optical intensity modulating device 300 further comprises a second optical waveguide grating and a second optical routing device. The second optical waveguide grating in this example is a second FBG 308. The second optical routing device in this example is a second optical circulator 306.

[0043] The third port 3 of the optical circulator 206 is connected to the first port 1 of the second optical circulator by an output optical fiber 216 of the optical circulator 206. The second optical circulator is configured to route the optical signal from the first port to a second port 2 to which is connected a third optical fiber 310 containing a second FBG 308. The optical signal reflected from the first FBG 208 includes a reflected portion of the upper sideband and possibly a small fraction of the optical carrier signal and the lower sideband, and is thus guided by the second optical circulator to the second FBG.

[0044] The second FBG 308 has a central reflection wavelength that corresponds to the upper sideband in this example. The second FBG 308 may have approximately the same reflection profile as the first FBG 208. Depending on the reflectivity of the second FBG, a predetermined percentage of the upper sideband is reflected by the second FBG, which is typically in the range of 90% to 99%. The optical carrier signal and lower sideband in the optical signal reflected from the first FBG 208 are transmitted by the second FBG toward a second optical dump 312 at the end of the third optical fiber 310. Depending on the reflectivity profile of the second FBG, a small percentage (e.g., 0.01% to 1%) of the optical carrier signal and lower sideband may be reflected by the second FBG.

[0045] The second optical circulator 306 is configured to route the optical signal reflected from the second FBG 308 from the second port 2 to the third port 3 to an output optical fiber 316 to form an output optical signal. The output optical signal from the optical circulator 306 may be provided as an input to an optical amplifier (not shown in this embodiment) via the output optical fiber 316.

[0046] In one embodiment, the first FBG 208 and the second FBG 308 are apodized FBGs with a ridged Gaussian reflection profile and a constant grating period. The first FBG 208 and the second FBG 308 may be mounted on an aluminum substrate with a temperature sensor and a piezoelectric actuator to control and stabilize their center reflection wavelengths.

[0047] 4, the optical intensity modulation device 400 further comprises an output optical waveguide grating, in this example a further FBG 402. The output from said grating 402 may be provided as an input to an optical amplifier (not shown in this embodiment) via an optical fiber.

[0048] As described above, the first FBG 208 has a reflectivity profile that includes a center reflection wavelength that corresponds to the upper sideband in this example. Depending on the reflectivity of the first FBG 208, a predetermined percentage of the upper sideband is reflected by the FBG 208. Depending on the reflectivity profile of the first FBG, the optical carrier signal and a small percentage (e.g., 0.01% to 1%) of the lower sideband are reflected by the first FBG 208.

[0049] The output FBG 402 may have a reflection bandwidth that includes the carrier wavelength and the lower sideband wavelength. The output FBG 402 is provided to a third optical fiber 404 connected to the third port 3 of the optical circulator 206. The output FBG therefore receives the optical signal reflected by the FBG 208. The output FBG 402 transmits the upper sideband received from the first FBG 208 to form an output optical signal, and reflects a predetermined percentage of the optical carrier signal and the lower sideband depending on the reflectivity of the output FBG, which is typically in the range of 90% to 99%.

[0050] 3 further comprises an output optical waveguide grating, for example a further FBG 402 as described above, after the second optical circulator 306. The output from the optical circulator 306 may be provided as an input to an optical amplifier (not shown in this embodiment) via an output optical fiber 316.

[0051] One embodiment provides an optical modulation device 500 as shown in Figure 5. In this embodiment, the optical modulator is a single sideband modulator SSBM 502. The SSBM operates to modulate a cw optical carrier signal to generate a single sideband, e.g., an upper sideband, on the optical carrier signal.

[0052] The first optical waveguide grating OWG 108 has a center reflection wavelength that corresponds to the generated sideband, in this example the upper sideband. One embodiment provides an optical modulation device 600 as shown in Figure 6. In this embodiment, the optical modulator is an acousto-optic modulator (AOM) 602.

[0053] The AOM602 has a carrier wavelength of λ c The AOM is arranged to receive a cw optical carrier signal of wavelength λ . The AOM is driven by an RF drive signal from an RF signal generator 104. The AOM modulates the optical carrier signal to produce an upper sideband wavelength λ . u The upper and lower sideband wavelengths λ l The RF drive signal is at frequency f, so the sideband is spaced from the carrier wavelength by an optical frequency offset f.

[0054] One embodiment provides an optical modulation device 700 shown in Figure 7. In this embodiment, an RF signal generator 704 operates to provide an RF drive signal including RF signal pulses having a compensation pulse shape. The RF drive signal thus causes one or more sidebands generated by the optical modulator 104 to include optical pulses having a compensation pulse shape. The compensation pulse shape is configured to compensate for the non-uniform gain response of the optical amplifier in the time domain.

[0055] Referring to FIG. 8, one embodiment provides a laser system 800 comprising a light source 802 and an optical intensity modulation device 100, as described above. The light source may be configured to generate a continuous wave (cw) optical carrier signal at the carrier wavelength. The light source may be a laser, such as a single-frequency fiber laser. The laser may have low phase noise and a narrow linewidth. Furthermore, it may have stable single-frequency operation. The laser may include a gain medium, and a rare-earth doped fiber is used as the gain medium. As an example, the gain medium may include a fiber doped with erbium (Er), ytterbium (Yb), or thulium (Tm). The examples given for the light source apply to other embodiments disclosed herein. Other light sources and lasers are contemplated without departing from the scope of the present disclosure. In some embodiments, the laser system includes only one modulator, such as an electro-optic modulator (EOM).

[0056] Referring to FIG. 9, one embodiment provides a laser system 900 comprising a light source 802, an optical intensity modulation device 700 as described above, and an optical amplifier 902. The optical source may be configured to generate a continuous wave (cw) optical carrier signal at the carrier wavelength, as shown in inset graph (a).

[0057] The optical amplifier may be configured to amplify the intensity-modulated output optical signal from the optical intensity modulation device 700. The optical amplifier has a non-uniform gain response in the time domain. The RF signal generator 704 operates to provide an RF drive signal including RF signal pulses having a compensation pulse shape. The RF drive signal thus causes one or more sidebands generated by the optical modulator 704 to include optical pulses having a compensation pulse shape, as shown in inset graph (b). The compensation pulse shape is configured to compensate for the non-uniform gain response in the time domain of the optical amplifier 902. Thus, the optical signal output from the optical amplifier includes optical pulses having the desired pulse shape, as shown in inset graph (c). The compensation optical pulses and corresponding optical pulses having the desired pulse shapes are illustrated in FIGS. 17-18.

[0058] Referring to FIG. 10, one embodiment provides a laser system 1000 comprising a light source 802 , an optical intensity modulator 1020 , an optical amplifier 902 , and a photodetector 1002 . The optical source may be configured to generate a continuous wave (cw) optical carrier signal at the carrier wavelength, as shown in inset graph (a).

[0059] Similar to the apparatus 100 described above, the optical intensity modulation apparatus 1020 comprises an optical modulator 102, an optical routing device 106, and an optical waveguide grating (OWG) 108. The optical intensity modulation apparatus 1020 also comprises an RF signal generator 1004 having a structure and operation described below.

[0060] The optical amplifier 902 is configured to amplify the intensity modulated output optical signal from the optical intensity modulator 1020. The optical amplifier has a non-uniform gain response in the time domain. The optical detector 1002 is configured to detect the pulse shape of the intensity-modulated output optical signal after amplification by the optical amplifier, and is further configured to generate an output signal indicative of the detected pulse shape.

[0061] The RF signal generator 1004 operates to provide an RF drive signal that includes RF signal pulses having a compensated pulse shape. The RF signal generator comprises an interface circuit 1006, a processor 1008, and a memory 1010. The memory contains instructions 1012 executable by the processor that cause the RF signal generator to operate as follows.

[0062] The RF signal generator is operative to receive an output signal from the photodetector, the output signal being indicative of the pulse shape detected by the photodetector. The RF signal generator is operative to determine a difference between the detected pulse shape and a target pulse shape and to determine a compensation pulse shape configured to at least partially compensate for the difference.

[0063] The RF signal generator operates to generate an RF drive signal including an RF signal pulse. The RF signal pulse has a compensation pulse shape. Thus, the RF drive signal causes one or more sidebands generated by the optical modulator 102 to include an optical pulse having the compensation pulse shape, as shown in insert graph (b). The compensation pulse shape is configured to compensate for the non-uniform gain response in the time domain of the optical amplifier 902. Thus, the optical signal output from the optical amplifier includes an optical pulse having the desired pulse shape, as shown in insert graph (c).

[0064] Referring to FIG. 11, one embodiment provides a quantum computing system 1100 comprising a light source 802, an optical intensity modulation device 100, and a containment chamber 1102. The optical source may be configured to generate a continuous wave (cw) optical carrier signal at the carrier wavelength.

[0065] The optical intensity modulator 100 is described above, it being understood that the optical intensity modulator 700 may be used instead. The confinement chamber may be an ion trap for confining ions, and the output optical signal from the optical intensity modulator 100 is delivered to the ion trap to interact with the trapped ions, for example, to store qubits in stable electronic states of the ions or to induce coupling between qubit states.

[0066] Alternatively, the confinement chamber may be an atom trap for confining atoms, and the output optical signal from the optical intensity modulation device 100 is delivered to the atom trap and interacts with the trapped atoms.

[0067] It will be appreciated that the optical intensity modulation device 700 may be used instead. The optical intensity modulator 1020 described above may also be used. Referring to FIG. 12, one embodiment provides a system 1200 for coherent excitation comprising a light source 802, an optical intensity modulation device 100, and an excitation chamber 1202.

[0068] The optical source may be configured to generate a continuous wave (cw) optical carrier signal at the carrier wavelength. The optical intensity modulator 100 is described above, it being understood that the optical intensity modulator 700 may be used instead.

[0069] The output optical signal from the optical intensity modulation device 100 is delivered to an excitation chamber and interacts with a sample in the excitation chamber. For example, the sample may include atoms such as cesium, strontium, or ytterbium atoms that undergo Rydberg excitation. In an alternative example, the excitation chamber is for performing Ramsey spectroscopy on the sample.

[0070] 13, one embodiment provides a system 1300 for coherent state control of a quantum system. The apparatus 1300 includes a light source 802, an optical intensity modulation device 100, and an interaction chamber 1302 for the quantum system.

[0071] The optical source may be configured to generate a continuous wave (cw) optical carrier signal at the carrier wavelength. The optical intensity modulator 100 is described above, it being understood that the optical intensity modulator 700 may be used instead.

[0072] The output optical signal from the optical intensity modulation device 100 is delivered to an interaction chamber to interact with one or more particles, e.g., one or more atoms, one or more ions, to control the quantum state of the one or more particles.

[0073] In some embodiments, the quantum system is selected from the group consisting of an atomic clock, an atomic interferometer, a quantum computer, a quantum gyroscope, or a quantum gravimeter. In general, optical intensity modulation devices can find applications within the fields of atomic, molecular, and optical physics (AMO). In particular, the disclosed device is suitable for applications requiring well-defined optical pulses, for example, to control optical or quantum gates. Such applications typically require complete control of the phase, shape, and energy of the delivered optical pulses. However, other applications are envisioned without departing from the scope of the present invention.

[0074] 14, one embodiment provides an optical intensity modulation device 1400 comprising an optical modulator 102, a radio frequency (RF) signal generator 104, and a first optical waveguide grating 208. In this embodiment, the optical routing device is a beam splitter 1418. The RF signal generator operates to provide an RF drive signal to the optical modulator.

[0075] The optical modulator 102 is a modulator of a carrier wavelength λ cThe optical modulator is configured to receive a cw optical carrier signal of wavelength λ. The optical modulator is driven by an RF drive signal from an RF signal generator 104 and phase-modulates the cw optical carrier signal. The optical modulator modulates the optical carrier signal to phase-modulate the upper sideband wavelength λ onto the optical carrier signal. u The upper and lower sideband wavelengths λ l The RF drive signal is at frequency f, so the sideband is spaced from the carrier wavelength by an optical frequency offset f.

[0076] The output of the optical modulator follows a first optical path 1420 of the optical intensity modulation device to an optical beam splitter 1418. The optical beam splitter is arranged to route the optical signal from the first optical path to a second optical path 1422 in which a first optical waveguide grating 208 is arranged. Thus, the optical carrier signal, upper sideband, and lower sideband output from the optical modulator are directed by the optical beam splitter to the first optical waveguide grating.

[0077] The first optical waveguide grating 208 has a reflectivity profile that includes a central reflection wavelength corresponding to the upper sideband in this example. Depending on the reflectivity of the first optical waveguide grating, a certain percentage of the upper sideband is reflected by the first optical waveguide grating, typically in the range of 90% to 99%. The optical carrier signal and the lower sideband are transmitted by the first optical waveguide grating toward an optical dump 214 at the end of the second optical path. As an example, the optical dump 214 may be implemented as an optical isolator. Alternatively, the optical dump 214 may be implemented as a fiber pigtail or an angled fiber cleave with graphite tape applied to absorb light. Depending on the reflectivity profile of the first optical waveguide grating, a small percentage (e.g., 0.01% to 1%) of the optical carrier signal and the lower sideband may be reflected by the optical waveguide grating.

[0078] The optical beam splitter 206 is configured to route the optical signal reflected from the first optical waveguide grating along the second optical path to the third optical path 1424 to form an output optical signal.

[0079] It will be appreciated that the optical path may be defined, at least in part, by an optical waveguide, such as an optical fiber. The optical path may be defined, at least in part, by free space optics. The RF signal generator operates to switch the drive signal on and off. When the drive signal is on, an upper sideband and a lower sideband are generated; when the drive signal is off, no sidebands are generated. In this example, when the drive signal is on, the upper sideband is present and is reflected by the first optical waveguide grating and directed toward the output as an output optical signal. By switching the drive signal on and off, an intensity-modulated output optical signal at the upper sideband wavelength is formed. The output optical signal may include two or more optical pulses with a phase difference, such as π / 2 or π, induced by the electro-optic modulator.

[0080] In one embodiment, the first optical waveguide grating 208 is an apodized optical waveguide grating with a ridged Gaussian reflection profile and a constant grating period. The first optical waveguide grating 208 may be mounted on an aluminum substrate with a temperature sensor and a piezoelectric actuator to control and stabilize its center reflection wavelength.

[0081] Referring to Figures 15 and 16, these show two graphs with experimental data for an optical intensity modulation device according to the present disclosure. The data are presented as two graphs showing the fall time and rise time, respectively, of the optical intensity modulation device. Both graphs show the photodetector (PD) signal (V) versus time (ns). It can be seen that the optical intensity modulation device provides very fast fall and rise times, less than 1 ns or even less than 900 ps. It can even be faster than this, somewhat limited by the choice of detector. Here, the rise time is defined as the time between 10% and 90% PD signals, as measured by the photodetector.

[0082] Referring to Figure 17, this graph shows the shape of an optical pulse having a compensation pulse shape configured for the non-uniform gain response of an optical amplifier in the time domain. The graph shows the photodetector (PD) voltage, signal (mW) versus time (ns). The pulse duration of the optical pulse is approximately 400 ns.

[0083] Referring to Figure 18, this graph shows the shape of an optical pulse output from an optical amplifier, which has a non-uniform gain response in the time domain. The amplifier received as input the optical pulse shown in Figure 17. The optical pulse output by the amplifier appears to be approximately rectangular in shape. The pulse duration is similar to the input pulse, but the peak power of the pulse is significantly amplified.

[0084] Referring to FIG. 19, this graph shows the reflection spectrum of a first optical waveguide grating according to the present disclosure. The graph shows the reflected power (mW) from the optical waveguide grating versus temperature (°C). This data is for a grating mounted on an aluminum substrate with a temperature sensor and piezoelectric actuator to stabilize its center reflection wavelength. Advantageously, the frequency of the RF drive signal is selected to correspond to a minimum in the reflection spectrum. This has the technical effect of providing a higher extinction ratio for the optical intensity modulation device. Note that while the graph shows power versus temperature, the graph has a similar appearance when plotted as reflected power versus reflected wavelength or reflected power versus reflected frequency. In other words, the reflection wavelength of the grating increases or decreases linearly with the temperature of the grating; therefore, the shape of the graph is the same.

[0085] List of Items Item 1. An optical intensity modulation device (100, 200, 300, 400, 500, 600, 700), an optical modulator (102, 202, 502, 602) operative to modulate a continuous wave (cw) optical carrier signal at a carrier wavelength to generate one or more sidebands on said optical carrier signal; a radio frequency (RF) signal generator (104, 704) operative to provide an RF drive signal to the optical modulator; a first optical waveguide grating (108, 208) having a center reflection wavelength corresponding to said sideband; an optical routing device (106, 206) configured to direct the optical carrier signal and the one or more sidebands to the first optical waveguide grating and to direct an optical signal reflected from the first optical waveguide grating towards an output to form an output optical signal; The apparatus, wherein the RF signal generator is operative to switch the drive signal on and off to form an intensity modulated output optical signal.

[0086] Item 2. The device of item 1, wherein the first optical waveguide grating is a first fiber Bragg grating (208). Item 3. The apparatus of item 2, wherein the first fiber Bragg grating is an apodized fiber Bragg grating having a raised Gaussian reflection profile and a constant grating period.

[0087] Item 4. The device according to any one of Items 1 to 3, wherein the first optical waveguide grating has a reflection bandwidth equal to or less than the frequency of the RF drive signal. Item 5. The device according to any one of items 1 to 4, wherein the first optical waveguide grating has a reflection bandwidth of less than 1 nm.

[0088] Item 6. The device of any one of items 1 to 5, wherein the first optical waveguide grating has a reflection bandwidth of about 10 pm to about 100 pm. Item 7. The device according to any one of items 1 to 6, wherein the optical routing device is an optical circulator (206).

[0089] Item 8. The device described in any one of Items 1 to 7, further comprising an output optical waveguide grating provided after the optical routing device, the output optical waveguide grating having a reflection bandwidth that includes the carrier wavelength.

[0090] Item 9. The device described in any one of Items 1 to 8, wherein the optical modulator and the optical routing device are arranged along a first optical path, and the optical routing device and the first waveguide grating are arranged along a second optical path, and the second optical path does not include an optical waveguide grating having a center reflection wavelength corresponding to the carrier signal or other generated sidebands other than the sidebands.

[0091] Item 10. A second optical waveguide grating (308) having a center reflection wavelength corresponding to the sideband; Item 10. The apparatus of any one of items 1 to 9, further comprising: a second optical routing device (306) configured to direct the reflected optical signal from the first optical waveguide grating to the second optical waveguide grating and to direct a second reflected optical signal from the second optical waveguide grating towards the output.

[0092] Item 11. The device of item 10, wherein the second optical waveguide grating is a second fiber Bragg grating (308). Item 12. The device of item 11, wherein the second fiber Bragg grating is an apodized fiber Bragg grating having a raised Gaussian reflection profile and a constant grating period.

[0093] Item 13. The device according to any one of Items 10 to 12, wherein the second optical routing device is a second optical circulator (306). Item 14. The device described in any one of Items 10 to 13, further comprising an output optical waveguide grating (402) provided after the second optical routing device, the output optical waveguide grating having a reflection bandwidth that includes the carrier wavelength.

[0094] Item 15. The device of item 8 or 14, wherein the output optical waveguide grating is a further fiber Bragg grating (402). Item 16. The optical modulator (102, 602) operates to modulate the cw optical carrier signal to generate a lower sideband and an upper sideband on the optical carrier signal; Item 16. The device according to any one of items 1 to 15, wherein the first optical waveguide grating has a center reflection wavelength corresponding to one of the lower sideband or the upper sideband.

[0095] Item 17. When citing items 8, 14, or 15, the device described in item 16, wherein the output optical waveguide grating (402) has a reflection bandwidth that includes the carrier wavelength and the other of the upper sideband or the lower sideband.

[0096] Item 18. The optical modulator is a single sideband (SSB) modulator (502) that operates to modulate the cw optical carrier signal to generate a single sideband on the optical carrier signal; Item 18. The apparatus according to any one of items 1 to 17, wherein the first optical waveguide grating (108) has a central reflection wavelength corresponding to the generated sideband.

[0097] Item 19. The device of any one of Items 1 to 18, wherein the RF signal has a frequency up to 100 GHz, such as a frequency in the range of 1 GHz to 20 GHz. Item 20. The device according to any one of Items 1 to 19, wherein the reflection bandwidth of the first optical waveguide grating is equal to or less than the frequency of the RF signal.

[0098] Item 21. The apparatus described in any one of Items 1 to 20, wherein the RF signal generator (704) operates to provide an RF drive signal including an RF signal pulse having a compensation pulse shape, and the one or more sidebands include an optical pulse having the compensation pulse shape, and the compensation pulse shape is configured to compensate for a non-uniform gain response of an optical amplifier in the time domain.

[0099] Item 22. The apparatus of item 21, wherein the compensation pulse shape has an amplitude envelope having a leading edge and a trailing edge, the amplitude increasing between the leading edge and the trailing edge. Item 23. The apparatus of Item 21 or 22, wherein the amplitude of the compensation pulse increases nonlinearly over at least a portion of the amplitude envelope between the leading edge and the trailing edge.

[0100] Item 24. The apparatus of any one of Items 21-23, wherein the amplitude increases approximately exponentially over at least a portion of the amplitude envelope between the leading edge and the trailing edge.

[0101] Item 25. A laser system (800, 900, 1000), a light source (802) configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength; A laser system comprising: an optical intensity modulation device (100, 700) according to any one of items 1 to 16.

[0102] Item 26. A quantum computing system (1100), a light source (802) configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength; A light intensity modulation device (100) according to any one of items 1 to 14, A quantum computing system comprising: a confinement chamber (1102).

[0103] Item 27. A system (1200) for coherent excitation, comprising: a light source (802) configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength; A light intensity modulation device (100) according to any one of items 1 to 16, an excitation chamber.

[0104] Item 28. A system (1300) for coherent state control of a quantum system, a light source (802) configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength; A light intensity modulation device (100) according to any one of items 1 to 16, an interaction chamber (1302) for the quantum system.

[0105] Item 29. The light intensity modulation device (1020) is the device according to any one of items 1 to 21, an optical amplifier (902) configured to amplify the intensity modulated output optical signal from the optical intensity modulation device, the optical amplifier having a non-uniform gain response in the time domain; an optical intensity modulation device (1002) configured to detect a pulse shape of the intensity-modulated output optical signal after amplification by the optical amplifier, and to generate an output signal indicative of the detected pulse shape; The RF signal generator (1004) comprises an interface circuit (1006), one or more processors (1008), and a memory (1010) comprising instructions executable by the processors, whereby the RF signal generator: receiving an output signal from the photodetector indicative of the detected pulse shape; determining a difference between the detected pulse shape and a target pulse shape; determining a compensation pulse shape configured to at least partially compensate for the difference; so that the one or more sidebands comprise optical pulses having the compensated pulse shape. 29. The system of any one of items 25 to 28, operable to: generate the drive signal including the RF signal pulse having the compensated pulse shape.

Claims

1. An optical intensity modulation device (100, 200, 300, 400, 500, 600, 700), an electro-optic modulator (102, 202, 502, 602) operative to modulate a continuous wave (cw) optical carrier signal at a carrier wavelength to generate one or more sidebands on said optical carrier signal; a radio frequency (RF) signal generator (104, 704) operative to provide an RF drive signal to said electro-optic modulator; a first optical waveguide grating (108, 208) having a center reflection wavelength corresponding substantially to said sideband; an optical circulator (106, 206) configured to direct the optical carrier signal and the one or more sidebands into the first optical waveguide grating and to direct an optical signal reflected from the first optical waveguide grating towards an output to form an output optical signal, the reflected optical signal including the one or more sidebands; The apparatus, wherein the RF signal generator is operative to switch the drive signal on and off to form an intensity modulated output optical signal.

2. The apparatus of claim 1 , wherein the first optical waveguide grating is a first fiber Bragg grating (208).

3. 3. The apparatus of claim 2, wherein the first fiber Bragg grating is an apodized fiber Bragg grating having a raised Gaussian reflection profile and a constant grating period.

4. Apparatus according to any one of claims 1 to 3, wherein the optical intensity modulator is configured to modulate the optical carrier signal with respect to both phase and amplitude.

5. The apparatus of claim 4 , wherein the optical intensity modulator is configured to control the phase and the amplitude independently of each other.

6. An apparatus according to any preceding claim, wherein the phase of the modulated output optical signal corresponds to the phase of the RF drive signal.

7. 7. Apparatus according to any preceding claim, wherein the one or more sidebands are spaced from the carrier wavelength by an optical frequency offset, the frequency offset corresponding to the frequency of the RF drive signal.

8. The apparatus of any one of claims 1 to 7, wherein the first optical waveguide grating has a reflection bandwidth less than or equal to the frequency of the RF signal.

9. The device according to any one of claims 1 to 8, wherein the first optical waveguide grating has a reflection bandwidth of between 1 GHz and 10 GHz at the carrier wavelength.

10. The apparatus according to any one of claims 1 to 9, wherein the output optical signal comprises two or more optical pulses having a phase difference, such as π / 2 or π, induced by the electro-optical modulator.

11. The apparatus of any one of claims 1 to 10, wherein the optical intensity modulator provides an extinction ratio of the output optical signal greater than 30 dB.

12. The apparatus of any one of claims 1 to 11, wherein the optical intensity modulation device provides a rise time of less than 1 ns.

13. the electro-optic modulator (102, 202, 502) is operative to modulate the cw optical carrier signal to generate a lower sideband and an upper sideband on the optical carrier signal; The apparatus of any one of claims 1 to 12, wherein the first optical waveguide grating has a central reflection wavelength corresponding to one of the lower sideband or the upper sideband.

14. 14. The apparatus of claim 13, wherein one or both of the lower sideband and the upper sideband are spaced from the carrier wavelength by an optical frequency offset, the frequency offset corresponding to the frequency of the RF drive signal.

15. 15. The apparatus of claim 14, wherein the optical frequency offset corresponds approximately to the reflection bandwidth of the first optical waveguide grating.

16. 16. The apparatus of any one of claims 1 to 15, wherein the electro-optical modulator is a single sideband modulator (SSBM) (502) operative to modulate the cw optical carrier signal to generate a single sideband on the optical carrier signal.

17. The apparatus of any preceding claim, wherein the RF signal has a frequency in the range of 1 GHz to 20 GHz.

18. 18. The apparatus of claim 1, wherein the RF signal generator (704) is operative to provide an RF drive signal comprising RF signal pulses having a compensation pulse shape, and wherein the one or more sidebands comprise optical pulses having the compensation pulse shape, the compensation pulse shape configured to compensate for a non-uniform gain response of an optical amplifier in the time domain.

19. A laser system (800, 900, 1000) comprising: a light source (802) configured to generate a continuous wave (cw) optical carrier signal at a carrier wavelength; A laser system comprising an optical intensity modulation device (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 18.

20. 20. The laser system of claim 19, wherein the light source provides an optical carrier signal having a long coherence length, the phase of the signal being well-defined over a long period of time.

21. 21. The laser system of claim 19 or 20, wherein the light source (802) is a single frequency fiber laser.

22. The laser system of any one of claims 19 to 21, further comprising an optical amplifier (902) configured to receive the intensity modulated output optical signal as an input.

23. 23. The laser system of claim 22, wherein the output optical signal from the optical amplifier (902) comprises one or more substantially rectangular pulses in the time domain.

24. 24. The laser system of claim 23, wherein each pulse has a well-defined energy and optical phase, and the optical signal is suitable for quantum applications such as for controlling quantum states.

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