Preheat the oven to 350 degrees F (175 degrees C).

Bring a large pot of lightly salted water to a boil. Add lasagna noodles and cook until tender yet firm to the bite, 8 to 10 minutes; drain.

Place frozen spinach and 1/2 cup water in a 2-quart nonstick saucepan; bring to a boil. Reduce heat to medium-high, cover, and cook, stirring occasionally, until spinach is tender, 6 to 7 minutes. Drain and squeeze out any excess water.

Stir together chicken and 1 jar Alfredo sauce in a medium bowl until well combined.

Mix together ricotta and spinach in a second medium bowl until well combined.

Arrange a single layer of lasagna noodles in a 9x13-inch baking dish, edges overlapping. Pour chicken-Alfredo mixture over noodles and spread evenly. Sprinkle with 1 cup mozzarella. Cover with another layer of noodles. Spread spinach mixture evenly over noodles. Pour 1/2 of the remaining jar of Alfredo sauce over spinach mixture and spread evenly. Sprinkle with 1 cup mozzarella. Lay on a final noodle layer and top with remaining 1/2 jar Alfredo sauce and 2 cups mozzarella. Season with salt and pepper.

Bake in the preheated oven until the top is brown and bubbly, 50 to 60 minutes.