Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia StrategyP-15

Multiple Photon Photon Resonance by Using Active-Multimode Interferometer
Laser Diode
Bingzhou Hong*, Takuya Kitano, Tomotaka Mori, Haisong Jiang, and Kiichi Hamamoto
1

Interdisciplinary Graduate School of Engineering, Kyushu University
Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan*3ES16013N@s.kyushu-u.ac.jp

Abstract
Active-multimode interferometer laser diode that integrates at least six oscillating cavities has beenachieved successfully. Multiple cavities contribute to multiple longitudinal mode spacings as well as
multiple PPR frequencies. Device aiming 100 GHz bandwidth design principle is proposed.

1. Introduction
Utilizing photon photon resonance(PPR) can extend direct modulation
bandwidth [1-3]. In this work, we reportmultiple PPRs using active-multimodeinterferometer laser diode (active-MMI LD).
The most important issue to achieve
multiple PPRs is to integrate multiple
longitudinal cavities within single laser.
Main cavities and inner cavities (causedfrom the high-mesa waveguide structure)contribute to complex cavities as well as
free space ranges (FSRs). Multiple
longitudinal wavelength differences exist inemission spectrum, which directly lead tomultiple
PPR
frequencies.
Directmodulation bandwidth up to at least 34 GHz
is successfully confirmed. Proposal of newdevice aiming 100 GHz bandwidth is also
given.

(a)Fig. 1 Device structure

frequency. Figure 1 (b) shows opticalpropagation path calculated by beam
propagation method (BPM). Optical power
distributes in 3 ports equally. Meanwhile,
optical loss at joint position are supressedbecause of such design. High mesa structure isused for waveguide structure. Previous
active-MMI LD demonstrate that high mesa
structure enables inner reflection at the edge ofMMI section [5], which contributes to inner
oscillating cavity. Thus, at least three more
oscillation cavities exist (inner cavity area inFig. 1(a)). The two curved waveguides andstraight waveguide together with MMI section
consist the three inner cavities (red dot lines).
Consequently, at least 6 different FSRs exist.
Moreover, slightly mismatch of these FSRs
generates much more wavelength difference
when compared to the case only two FSRs
exist.

2. Device design
The device structure is shown in Fig.1(a). Twocurved-waveguides and straight waveguide areconnected to MMI section of 10 μm width.
Radii and bending angles are slightly different
to ensure cavity length with slightly difference.
Width of both straight waveguide and bending
waveguide is 2 μm. Designed modulation
section length is 50 μm. As shown in Fig. 1,
1 by 3 -MMI are designed (main cavities,black solid lines). Each cavity lengthcorresponds to a FSR. Mismatch and overlap
between each FSR generate different
wavelength differences. Delicate wavelength
mismatch arrangement lead to preferred PPR44

Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy

P-15
differences clearly indicate the existence ofmultiple PPRs in the small signal response.
Note the fact that not all wavelengths thatmight induce PPR are visible, and thatmeans at least 6 higher order resonancepeaks must be observed in frequency
response (FR). Measured FR results areshown in Fig. 3. Multiple higher order PPR
peaks are clearly observed. Damping
between peaks are suppressed because ofmultiple PPR. The modulation bandwidth isextended to at least 34 GHz in Fig. 3. Suchbandwidth may provide direct modulation
speed of at least 45 Gbps. The frequency
resonance peaks reflect exact thelongitudinal mode spacing itself. The higherorder resonance peaks observed at 8 GHz,
10 GHz, 13 GHz, 19 GHz, 23 GHz and 36
GHz correspond to longitudinal wavelength
difference in Fig. 2(b). Such wavelength
differences are visible near main lasing peak.
Moreover, another several frequency
response peaks are observed in Fig. 3. This
indicates that more longitudinal mode
spacings must exist although they are notvisible in the static emission spectrum.

Optical Power [dBm]

3. Experimental results and discussion
0-1-2-3-4
1557.51558.0
Wavelength

1558.5

Optical Power [dBm]-5-40-42-44-46-48-50

1552.01552.5
Wavelength [nm]Fig. 2: (a) Central wavelength and (b)wavelengthapart from central lasing peak10Small signal respons [dB]1551.550-5-3 dB-10-15-20-25034
2030
10Frequency [GHz]Fig. 3: Measured small signal response40

4. Conclusion
Active-MMI LD with multiple PPRs
was demonstrated. Main and inner cavities
contribute to complex FSRs. Multiple
wavelength
differencesatcentralwavelength are observed.

Fig. 2 (a) shows the central wavelength
emission peak at 1558 nm. Obviously, thecentral wavelength peak consists of several
longitudinal modes and multiple adjacentpeaks are visible. Such sub-peaks are caused
from the FSR mismatch. It is, however,still difficult to judge exact longitudinalcavity components in side laser diodebecause some of them are merged with eachother at central wavelength. The mismatch ismuch more obvious at wavelength apartfrom central lasing peak. In Fig. 2 (c), themismatches are obvious at wavelength of1552 nm. At least 6 sub-peak components(wavelength differences) caused fromdifferent cavities exist at longer wavelength
side. This result reveals that complex
cavities indeed exist and overlap between
several FSRs generates multiple longitudinalmode spacings even if they are not visible at
central wavelength.
The wavelength

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