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Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities to explore fundamental physics and enable new measurements. However, their size and use of bulk components prevent them from being more widely adopted in applications that require precision timing. By leveraging silicon-chip photon...
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... of traditional electronic detectors, a requirement for producing a usable microwave clock signal. To circumvent this issue, our optical clock architecture employs two interlocked microcombs: a high repetition rate, octave-spanning comb used for self-referencing and a narrow-band comb used to produce an electronically detectable microwave output. Fig. 1a shows a schematic of the experiment. The local oscillator ("clock laser") for our clock is a 778.1 nm, distributed Bragg reflector (DBR) laser that is referenced to the two-photon transition in rubidium-87 in a microfabricated vapor cell. We generate a 1 THz repetition rate, octave-spanning, DKS frequency comb by coupling ≈100 mW of ...
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... spaced ruler to measure the repetition rate of the SiN comb. The output of the clock is a 22 GHz optical pulse train (and corresponding electrical signal) that is phase stabilized to the rubidium two-photon transition. The techniques for locking the DBR laser to the rubidium atoms and stabilizing the frequency combs are detailed in the Methods. Fig. 1 b, c, and d show images of the main components of the clock: the two microresonators and the Rb cell. All three elements are microfabricated devices and, in future implementations of the concept introduced here, would support more advanced integration. a, The microfabricated optical clock consists of an optical local oscillator, a ...
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... has been studied extensively for use as an optical frequency standard (27)(28)(29)(30). Here, we only discuss details of this system relevant to spectroscopy in a microfabricated vapor cell. The clock laser is locked to the 5S1/2 (F=2) to 5D5/2 (F=4) two-photon transition in rubidium-87 at 778.106 nm (385.284566 THz) using a 3×3×3 mm vapor cell (Fig. 1d). The rear window of the cell is covered with a high-reflectivity coating (R=99.8%) which is used to retroreflect the clock laser and provide the counter-propagating beams required to excite the Doppler-free, two-photon transition. The front window is anti- reflection coated on both sides to prevent parasitic reflections. Doppler-free ...
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... mW of the stabilized clock laser is sent though an optical fiber and used to stabilize the pump frequency of the two microcombs. Additionally, ≈1 mW of the clock light is directed into a second optical fiber and beat against an auxiliary 250 MHz repetition rate, erbium fiber frequency comb to directly monitor the clock laser optical frequency. Fig. 1c shows an image of the wedged, 21.97 GHz free-spectral range silica (SiO2) microresonator used to measure the repetition rate of our self-referenced Si3N4 microcomb. The design, fabrication and implementation of the silica comb has been described in detail elsewhere (36). Briefly, the microresonator is fabricated by thermally growing a ...
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... the microresonator is fabricated by thermally growing a layer of SiO2 on a Si substrate. The silica layer is then shaped into a wedge-resonator by lithographically patterning a photoresist material and etching the silica with a hydrofluoric acid solution. As a final step, the pedestal is formed by applying a XeF2 dry etch to the Si substrate. Fig. 1b shows an SEM image of the SiN microresonator which is described in detail in Briles et al. (25). The Si3N4 resonator is fabricated by first depositing a thin layer (≈615 nm) of Si3N4 on a thermally-oxidized silicon wafer using low-pressure, chemical-vapor deposition. The 46 μm diameter ring resonator and coupling waveguides are then ...
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... of traditional electronic detectors, a requirement for producing a usable microwave clock signal. To circumvent this issue, our optical clock architecture employs two interlocked microcombs: a high repetition rate, octave-spanning comb used for self-referencing and a narrow-band comb used to produce an electronically detectable microwave output. Fig. 1a shows a schematic of the experiment. The local oscillator ("clock laser") for our clock is a 778.1 nm, distributed Bragg reflector (DBR) laser that is referenced to the two-photon transition in rubidium-87 in a microfabricated vapor cell. We generate a 1 THz repetition rate, octave-spanning, DKS frequency comb by coupling ≈100 mW of ...
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... spaced ruler to measure the repetition rate of the SiN comb. The output of the clock is a 22 GHz optical pulse train (and corresponding electrical signal) that is phase stabilized to the rubidium two-photon transition. The techniques for locking the DBR laser to the rubidium atoms and stabilizing the frequency combs are detailed in the Methods. Fig. 1 b, c, and d show images of the main components of the clock: the two microresonators and the Rb cell. All three elements are microfabricated devices and, in future implementations of the concept introduced here, would support more advanced integration. a, The microfabricated optical clock consists of an optical local oscillator, a ...
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... has been studied extensively for use as an optical frequency standard (27)(28)(29)(30). Here, we only discuss details of this system relevant to spectroscopy in a microfabricated vapor cell. The clock laser is locked to the 5S1/2 (F=2) to 5D5/2 (F=4) two-photon transition in rubidium-87 at 778.106 nm (385.284566 THz) using a 3×3×3 mm vapor cell (Fig. 1d). The rear window of the cell is covered with a high-reflectivity coating (R=99.8%) which is used to retroreflect the clock laser and provide the counter-propagating beams required to excite the Doppler-free, two-photon transition. The front window is anti- reflection coated on both sides to prevent parasitic reflections. Doppler-free ...
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... mW of the stabilized clock laser is sent though an optical fiber and used to stabilize the pump frequency of the two microcombs. Additionally, ≈1 mW of the clock light is directed into a second optical fiber and beat against an auxiliary 250 MHz repetition rate, erbium fiber frequency comb to directly monitor the clock laser optical frequency. Fig. 1c shows an image of the wedged, 21.97 GHz free-spectral range silica (SiO2) microresonator used to measure the repetition rate of our self-referenced Si3N4 microcomb. The design, fabrication and implementation of the silica comb has been described in detail elsewhere (36). Briefly, the microresonator is fabricated by thermally growing a ...
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... the microresonator is fabricated by thermally growing a layer of SiO2 on a Si substrate. The silica layer is then shaped into a wedge-resonator by lithographically patterning a photoresist material and etching the silica with a hydrofluoric acid solution. As a final step, the pedestal is formed by applying a XeF2 dry etch to the Si substrate. Fig. 1b shows an SEM image of the SiN microresonator which is described in detail in Briles et al. (25). The Si3N4 resonator is fabricated by first depositing a thin layer (≈615 nm) of Si3N4 on a thermally-oxidized silicon wafer using low-pressure, chemical-vapor deposition. The 46 μm diameter ring resonator and coupling waveguides are then ...
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Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities for exploring fundamental physics and enabling new measurements. However, their size and the use of bulk components prevent them from being more widely adopted in applications that require precision timing. By leveraging silicon-ch...
