We believe a frequency comb should be stable and reliable in every situation
Frequency combs are the robust and reliable backbone of an experiment. This thought is guiding our frequency comb product development. It’s the shared vision with our customers, who want to focus more on the actual research and spend less time maintaining their system.
CERO technology – zero fceo
Our awarded CERO technology enables an inherently fCEO-stable frequency comb design that combines robustness with reliability and highest stability. The offset frequency fCEO of TOPTICA’s Difference Frequency Comb (DFC) is passively fixed to zero by utilizing a difference frequency generation (DFG) process for each optical pulse. This results in a reduced comb equation fn = fceo + n · frep and multiple advantages for your experiment:
Perfect lock to optical reference
By fixing fCEO to zero with the DFG process we achieve truly zero noise at the frequency origin and completely decouple fCEO and frep.
This is particularly beneficial when the comb is stabilized to an optical reference like a narrow linewidth laser. Then the frequencies of the comb lines are tightly locked at 0 Hz and, additionally, at a high optical frequency (100s of THz) by the optical reference. Here, the CERO technology has a clear advantage over the conventional f-to-2f comb approach, since it also cancels high frequency noise components of fCEO. Thus, all comb lines perfectly inherit the phase noise from the optical reference.
Having zero noise at 0 Hz also leads to zero error bar on the offset frequency fCEO. This allows for a more precise determination of the absolute laser frequency: fLaser = fCEO + n⋅frep ± fBeat
Ultra-low noise and narrow linewidth
The CERO technology uses a passive, all-optical phase-lock for stabilizing the offset frequency fCEO. By that our comb system requires one electronic locking loop less compared to conventional f-2f-combs. Hence, in TOPTICA’s frequency comb the fCEO contains no electronic noise (also not at high frequencies) which results in an unprecedented low carrier-envelope-phase (CEP) noise and a narrow free-running linewidth. With these properties TOPTICA’s DFC CORE + enables applications with stringent requirements on linewidth and phase noise.
100 times faster noise reduction
By utilizing a passive, all-optical lock the effective fCEO-locking-bandwidth of the DFC CORE + is as high as 200 MHz. By that it suppresses perturbations and noise 100 times faster compared to conventional f-2f-combs which are limited by the bandwidth of the electronic fCEO-stabilization. This makes TOPTICA’s Difference Frequency Comb more robust against external influences.
Additionally, the CERO Technology allows for a comb system with reduced complexity (one locking loop less) which is less prone to errors and therefore more reliable in daily use.
CEROテクノロジーとは？
オフセットフリー差周波コム（DFC)の動作原理は、低ノイズエルビウムファイバーモードロック共振器の出力による広帯域なスーパーコンティニュームの発生と、非線形結晶によるオクターブスパンのスペクトルの低周波部と高周波部間で生み出す光学差周波発生により成り立っています。最も重要な特徴は、卓越した安定性、シンプルかつ高い信頼性、全受動型周波数オフセットの安定化です。コムは、 そのオリジナルスペクトルの２つの部分の共通モードの抑制によって、オフセット位相及びオフセット周波数の変動から完全にフリーとなります。加えて、DFCのキャリアエンヴェロープオフセット周波数fCEOは、常にゼロに固定されます。
- Er3+-ファイバー共振器と非線形ファイバーによる広帯域スーパーコンティニュームの生成
- 非線形結晶内のスーパーコンティニュームの低周波と高周波スペクトル部間を用いた差周波生成
- 両スペクトル部は同一の fCEOを持ち相互にキャンセル
- 最終的にコムはキャリアエンベロープ位相を安定化し、fCEO をゼロに固定
- トプティカ社特許技術を採用 (DE102004022037)
fCEO-stabilization by difference frequency generation (DFG)
完全受動型光学系による fCEO の安定化は、一般的なf-2f干渉計によるアプローチ方法に対して、明確な利点を持ちます。これは、周波数計測分野 (Krauss et al., Opt. Lett, 36, 540 (2011))の数々の有名な研究者によって報告されています。受動安定化の最大の利点は、電気的なノイズによって制限されないことです。加えて、キャリアエンベロープのビート調整や複雑なドリフト補正の必要が無く、キャリアエンヴェロープオフセット ロッキング用のエレクトロニクスがないことにより、複雑な制御エレクトロニクスの必要性を著しく軽減できます。唯一の調整パラメーターは、DFCの繰り返し周波数です。最適な高周波(RF)リファレンスに、簡単に安定化できます。
- DFG in the literature
TOPTICAs frequency comb DFC shows quadratic scaling of the phase noise with frequency. This textbook like behavior has been shown to a remarkable degree. The DFC behaves like an elastic tape with a true fixpoint at zero. An ideal system to be combined with an optical reference. Characterization of a DFG comb showing quadratic scaling of the phase noise with frequency, T. Puppe et al., Optics Letters Vol. 41, Issue 8 (2016)
“The DFG comb possesses a vanishing carrier envelope offset frequency that permits the construction of a simple and thus potentially more stable optical clockwork.“ Zimmermann, Gohle, Holzwarth, Udem and Hänsch, Opt. Lett., 29, 310 (2004)
“This all passive approach provides extremely reliable and rigid locking of fCEO on both short and long time scales”, Krauss, Fehrenbacher, Brida, Riek, Sell, Huber, and Leitenstorfer, Opt. Lett., 36, 540 (2011)
“… in this nonlinear process the phases of the two pulses add up with different signs, leading to CEP cancellation and resulting in passive, all-optical phase stabilization.”Manzoni, Cerullo, and De Silvestri, Opt. Lett., 29, 2668 (2004)
“The unique feature … is that fCEO of the DF is zero without any servo-loop feedback system; i.e., the waveform is self-stabilized in the resultant pulse train.” “The generated phase-stable pulses may - after preamplification - be suitable for seeding high-gain Ti:sapphire amplifiers and (or) the oscillator itself.”Fuji, Apolonski and Krausz, Opt. Lett., 29, 632 (2004)